Downtown Toronto condo with no locker?

Yes it's normal, especially in today's market and investor purchased condos where they are looking to rent out or flip.

When we were purchasing our condos we were debating on whether to purchase a locker but were advised against it since it wouldn't be worth the extra cost in maintenance fees and you wouldn't get extra rent for it.

Does not affect resale value IMO. She can always rent one. They’re pretty cheap$50-100/ month. Also see some for sale. A lot of people do not buy them and so builders end up having to sell at a discount to get rid of them. Have seen that happen a number of times already.

I think the issue is also that unlike older condos where the size of the locker was pretty big (4x4, floor to ceiling) many of these now are literally the size of storage lockers that are the size of the storage lockers at Goodlife (or maybe slightly bigger).

What does she plan to use the locker for?

Does she need it for... winter tires? Sporting equipment?

It is best used for things that are not required frequently. I've heard of rare cases where someone has used it to store extra pantry items (paper towels, toilet paper, canned goods) but IMO, it is way too filthy and dusty for me to go down there regularly. I've only used mine for boxes that I dont' throw out in case I moved... lol... So I've held onto my original tv boxes to save a whopping $20-30 on buying a moving box for a tv.

Yes not a problem. If its a studio you are not meant to spend much time in it.. i doubt theres much storage space or much of a kitchen or countertop to cook or meal prep anyways.