I haven't watched season three yet, but god this is annoying. Either commission something for a set amount of seasons, or give them a heads up that this is going to be the last one. It's a shitty way to run a television service.
It puts people off starting investing/watching a new series because they think "I'll wait until it's finished and binge it." So people don't watch it, so it gets cancelled quicker. Or people don't bother to start something at all because they just assume it won't last.
I just finished watching all 4 seasons of The Last Man on Earth on Amazon Prime, I didn't realise a) that it was cancelled last year and b) it ended on a cliffhanger. Small comfort that the writers made it public what was going to happen, so at least we know, but it's just a stupid way to do things and a massive kick in the nuts to the people who make and work on these shows, and the audience, to have the plug pulled without a chance to finish the story properly. Would you sell a book with the last chapter missing?