FWIW there is only one winery where I’ve ever encountered any pressure to buy (a well-known Tuscan winery, where we’d already paid for the tasting!).
In general I try to arrange fewer winery visits on (Italian) holidays these days, so that it should be no problem buying at least a bottle in each we taste at. I recall someone saying here a few years ago that they thought it respectful to buy a bottle, unless none at all appealed/impressed. It’s advice that I felt right for me, though I’ve no problem with other takes on this. Even in one Veneto winery where the wines were generally unimpressive, the prices were at least reasonable and we bought a valpolicella that was handy to drink whilst we were there (a useful option when cargo hold allowances put pressure on what you can buy to take home). The wine was fine with the food I’d picked up in Verona. I wish the wines had been better as the winery people were very friendly / hospitable. One where I really wanted to like the wines, but it was not to be.