It's all volunteer work which means it would be hard to get enough staffs to spend their evenings at the barn instead of being with friends and family. The facility would need to be cleared out so some vehicles can return from service. Doors open prevents them from doing their maintenance work too. Although some of us wouldn't mind if we got a whole bunch of ALRVs on the 510 the next day can't they can't do their routine work. The 510 had more ALRVs than usual today with only one new car on the 509 on a Saturday.And on a side note, I'm really frustrated by the limited hours of Doors Open. The Jane's Walks went on all day long, ranging from early in the morning to late in the evening. They even had a bunch of them on Friday too. But with Doors Open, nothing is open earlier than 10:00 am, and everything closes by 5 pm at the latest. Some buildings are not even open on both days of the weekend, including Leslie Barns which is guaranteed to be popular (in fact the TTC will increase service on the Jones bus because of it).
With only a few hours a day, I never have time to visit more than a small handful of buildings by the time I travel to them, wait in line or do a tour. I probably won't have time to see Leslie Barns either because there are too many other building that I want to visit, and it's quite far from downtown.