> Block compilation in Common Lisp was and is used mostly for application delivery
The main place I've personally encountered people who care about block compilation in CL isn't so much delivery (as in, to an external client) as getting it ready to run "for real", mostly numerical stuff that is being prepared to run in batch mode on a giant dataset. I guess that's a kind of deployment though, even if the operator and developer is the same research group.
I could be imagining things, but one downside I think I see in not having block compilation in SBCL is that people writing numerical code targeting it have a tendency to pack as much as possible into flet and labels, using one big function as the poor man's compilation block (since within a single function most of CL's dynamic features aren't in play).
I tend not to like code like that when hacking on it. Besides often reading less clearly and sometimes leading to duplicate or near-duplicate code, separate functions are more flexible: they can be dynamically redefined while tinkering with things, they can be called on their own, etc. Of course, that's precisely why the compiler can't perform certain optimizations on full calls. But I think people would be more free with the defun if they knew the compiler would take care of optimizing everything when deployed.