> you have to add them yourself to be compatible with your dependencies
This is no more true for version upper bounds than it is for version lower bounds, assuming that package installers ensure all package version constraints are satisfied.
I presume you think version lower bounds should still be honoured?
The point is that you can know that a lower bound is necessary at the time of publication; an upper bound is either speculative or purely defensive, and has possibly unnecessary consequences for your dependents.
This is no more true for version upper bounds than it is for version lower bounds, assuming that package installers ensure all package version constraints are satisfied.
I presume you think version lower bounds should still be honoured?