Amen. I have never understood why people rent lenses either unless they either 1) are just a filmmaker on a single project 2) want to use a lens they cant afford or 3) a pro who is too cheap to invest in it because they would rather "bill it to production." To hell with group #3.
There are plenty of reasons to rent lenses:
to get the right focal length range and look for a project without making a huge investment
to be able to compare and test lenses in order to make that decision
to choose a lens size or weight that best suits the project
to make sure the lenses will all be properly collimated and in good condition
to access lenses immediately, without needing to spend time finding, purchasing, testing and possibly having to get them serviced
to have a back up if a lens is dropped or damaged
to try out different lenses
to access lenses that may be rare or otherwise hard to find
to use lenses that match a particular camera mount or format
to use specialty lenses like probes or macros or extreme telephotos or shift and tilts etc for specific shots
to access the knowledge bank and technical resources of rental house staff
to ensure that a production isn't dependent on a particular crew member for a vital part of the gear list
to ensure that questions of liability in case of damage and associated insurance are well understood
Some of these reasons may be more obvious to working professionals than someone trying to make their first feature on a very low budget. Clearly there is no single lens set that suits every project, and on many productions the cost of time lost due to faulty or inappropriate gear or desperately sourcing replacements is not a risk worth taking.
I'm not sure who you mean by the "pros" who you believe should invest in lenses - DPs, camera assistants, directors? - but calling them cheap because they won't cover costs that are rightfully production costs is ludicrous.
The better restaurant analogy is if you were running a restaurant and expected the waiters to bring all the cutlery and crockery and the chefs to bring all their own pots, pans and ovens.
(Edit: as Stuart just said.)