Speaking as a former snout...
In a previous life I was a journalist, and enjoyed quite a lot of 'corporate hospitality'. So I feel qualified to clarify here:
It's not about 'getting business done', it's about getting people to show up. Send me an invite to two press conferences on the same day, and all other things being equal, I'm going to accept the one that comes with a six-course meal at the Ritz, rather than the one with the cold buffet in a bleak meeting room in Newport Pagnell.
And having turned up, I'll meet the company's flacks, I'll know their names, I'll recognise their logo when I see it on their letterhead, and I'm that much more likely to take time to read it.
Corruption? Maybe. But it's more than common, it's virtually universal practice, and I have yet to hear of any country in the history of the world that has successfully outlawed it (though some have tried).