Their motivations are varied but, however irrational, the important thing for the economy is that they continue to come. Travel and tourism represent 5 per cent of our gross domestic product and contribute pounds 25bn to the economy annually. Last year, we welcomed 23.6 million visitors from overseas, who spent nearly pounds 12bn; and 87,800 new jobs were created, adding to the 1.5 million already in existence.
The decision of Heritage Secretary Virginia Bottomley not to renew the part-time contract of the director of the British Tourist Association and the English Travel Board, Adele Biss, announced on Monday, will not halt the industry in its tracks. Incoming tour operators predict 8.4 per cent growth this year, and if they turn out to be badly wrong, it is more likely to be the fault of the IRA than of Mrs Bottomley.
But Ms Biss's going, after only three years in the job, gives pause for thought. Within the industry, no one has anything but praise for her; perplexity at her sacking is likewise universal. One theory is that the two women just failed to hit it off. More plausibly it is suggested that Mrs Bottomley's department smarted under Ms Biss's relentless criticism of government underfunding, and fiercely resisted her attempt to increase the BTA's independence.
Coming into a business beset by amateurism, that had been kicked like a punctured football from one government department to another, Ms Biss brought marketing skills honed at Unilever, and a determination to hoist the industry's standards to international level. For all her good works - and there is a limit to the amount that anyone can do on two days a week - it's painfully clear from Mrs Bottomley's action that a punctured football is what the industry remains.
It is difficult to obtain a clear picture of the true state of Britain's tourist industry. From one perspective, given the many millions of visitors, it has never looked more prosperous. Yet Ms Biss has asserted that it is in long-term decline compared with other destinations for foreign visitors, while its appeal to the British themselves has been in absolute decline ever since we began forsaking our dunes and corrugated iron windbreaks for the Costa Brava. The number of jobs created in the industry suggests rude health, but there was a deficit of pounds 3.7bn between what British holidaymakers spent abroad last year, and what overseas visitors spent here.
The appearance of rude health is because, once they've got a bit of money in their pockets, milling around in large airplanes is how people all over the world like to spend it. Inevitably, a lot of them end up here. But, relative to many other countries, we are still on the slide.
The problem Ms Biss inherited and will pass on to her successor is that selling a country is an odd sort of business. It is a much more ticklish challenge than selling biscuits or whisky or superguns.
On the one hand, you have what your potential customers expect of the place, their preconceptions and prejudices: Beefeaters, castles, Shakespeare, golf, Big Ben. Shake these expectations too violently and you may turn people off altogether, causing them to drift away in bemusement. Ram them home too stolidly and you risk boring people to death.
On the other hand, you have the bewildering fragmentation of the industry itself: 120,000 small businesses, huge hotel chains, theme parks, souvenir shops, stately homes, beach resorts, festivals, caravan parks - all clamouring furiously to be promoted abroad. The job of the BTA was somehow to derive a tune from this horrible cacophony, and sing it in siren tones to potential customers.
The traditional solution to the problem was to let Britain market itself in the usual way, with Beefeaters, castles etc, and let the foreign johnnies like it or lump it. Besides being the least demanding, this approach accorded with the unspoken assumption that having foreigners swilling around our streets in large numbers was really a rather rum do, something to be tolerated rather than actively encouraged.
With Ms Biss's accession, all that was swept away: marketing analysts were drafted in from McKinsey to create a marketing strategy: "the branding of Britain to suit different market segments", as a source at the BTA puts it, which, stripped of jargon, is a sensible thing to do. The French, for example, are keen on shopping in Britain, and on street fashion; so don't sell them Big Ben but Camden market. Japan's "OLs" - so-called "office ladies" - flock to Europe, so lure them here by projecting a softer, more feminine image of the country, an approach pioneered with the successful "tea and roses" campaign. And so on.
The leap in visitor numbers last year suggests that this strategy is beginning to bite. The big question remains of how to sell Britain - and more particularly, England - to the British, and this is one that the cash-strapped English Travel Agency has only just made a start on. Even with global warming, bringing the British back to English beaches is a formidable challenge.
But even larger than that is the question of whether tourism is an industry the Government is minded to take seriously: whether it is to be forced to bumble on, chronically underfunded, chaotically structured, and guided by a part-timer, as hitherto; or whether its importance to the nation's economy is for the first time to receive proper financial recognition.
Ms Biss has done a heroic job of making bricks with the bare minimum of straw; but by trying to turn the BTA into a more serious and independently minded organisation, she seems to have paid with her job. The irony is that the reforms she was pressing for are exactly what the industry needs.