Agreed. But if a user agrees to be left "out in the cold", you should allow him to. Given that it is not very costly for you to prepare your software for on-prem, it maybe a win-win for all the parties involved.
Assuming you are not providing any updates (not even security critical ones for argument's sake), you only need to package and add documentation for an on-prem installation. Why is it so costly?
FUD. Among my products I have desktop software. Sure I got some pains upon initial release but it's been literally years since I really needed to test "for million configurations".
I also have experience developing and maintaining cloud solutions. Total amount of work that goes into large cloud apps and amount of things things that can brake or not work properly is fairly impressive. Definitely not any less then on premises
