...get picky why don't you.
Ooops. The nasties are on the march.
Really, condensing a lot of interesting - if fairly inconsequential - debate into an answer to the original question.................
Some folk have found variety of compelling reasons to upgrade from LR4 to LR5.
Other have not needed a compelling reason and have upgraded anyway.
Some don't feel like upgrading at present but might later on.
Whatever floats your boat, guys. (or any number of equally inane clichés)