I don't get why condo buildings don't simply have individual locked garages assigned to each unit.
simple answer is $$
They can paint 2 lines on the ground and sell a 3m x 6m parking space for $30k-$50k, if they were to build individual garages they would not be able to fit a garage unit into a 3m x 6m footprint, for arguments sake it'd have to be 25% larger, so they just went from 400 proposed spaces to 300 for example (approx $4M loss), they have to upgrade their fire alarm system to add individual zones for every unit, as well as their sprinkler system, plus cost of materials to build (thicker slab, more rebar, masonry walls, overhead doors, lighting, electrical, paint etc etc) so lets say on a production scale each garage unit costs them an extra $8k, so the added cost is $2.4M for the extra construction, so add the $4M they lost, so now they have to sell their remaining spots for and extra $22K just to break even, and developers are not in the "breaking even" business so your $30k-$50k parking space now costs closer to $100K
As for the original proposal to "build a few walls"...its not that simple, they cant build without permits (insurance co, and board wont allow, not to mention its illegal) so design costs, permit costs, walls, door, lighting, fire alarm modifications, power modifications, sprinkler system modifications, security system modifications etc etc etc i'd guess they are around $50k+ (on the conservative side) to retrofit a spot.