They're playing on loss aversion and the endowment effect. It feels worse to lose something than to never have it, so people are more willing to pay to keep it than they would be to pay to buy it if they were never given it in the first place.
In the end, though, when I discovered this was how it worked at the end of my PyCharm subscription, it left me quite a bitter taste in my mouth, and I just stopped purchasing any JetBrains products. These kind of details are akin to trying to trick people via putting stuff into EULAs nobody reads, and for me at least, it gives the distinct feeling that they're trying very hard to screw me over, so I try to not frequent nor support those kinds of businesses, IMHO.
I've been using them for awhile and I felt they were really up front about what they were doing, but I don't know if they've always been as transparent.
Initially JetBrains didn't even want to offer rollback licenses when they went to subscription only model a few years ago.
There was a big uproar among programmer communities (including here on HN) and after few weeks of deliberation a compromise of sorts was reached.
Despite offering a nice product line, JetBrains did lose a bunch of goodwill including mine. But goodwill does not pay the bills.
> The trick is that at the end of your yearly subscription you have already upgraded to a newer version, so falling back to the perpetual license means downgrading, which is both often a practical problem and (perhaps most importantly) something that I think many have an emotional aversion to.
Qualifies as
> a particularly hamfisted attempt to grab an almost negligible amount of money
OK, so maybe it's not as negligible an amount but it feels petty and I'd not pay money to a company that pulls stunts like that on its customers.
I'm pretty sure that if the fallback license was to the most recent version you're entitled to during your subscription way more people would take leaps between the end of a subscription and the start of the next one (though Jetbrains offers you a further discount if you don't do so).