"wasn't able" is dubious. Of course, there are repercussions for not moving out on the date, but it's not an imperative. If the landlord had to move his stuff to the curb, or it delayed closing on a house, that causes a cascade into another transaction. The world doesn't stop, of course. If the landlord is forced to pay movers to put your stuff in storage and send the bill to the tenant, those costs can, in theory, be passed on to the moving company. The details depend on the contract, obviously.

It can hurt your changes of getting your next house/apartment. Depending on where you are it might not be worth risking a bad mark on your rental history/burning bridges with a company that manages a huge number of properties.

Yeah, something important to file away in your book of life lessons is that you should _never_ schedule a move on the day you have to be out. Not unless you're backed into a corner with no alternative. Sometimes life throws you curveballs - for example in 2020 I had purchased a house and was scheduled to move, but my mom passed away around 6 PM the day before the move. Thankfully it was just an across-town move, and I had about 10 days to play with before the lease on my condo ended, and the moving company was able to reschedule for a week later.

> you should _never_ schedule a move on the day you have to be out

If you're switching apartments in a city, you usually don't have much of a choice.

Your lease ends at the end of the month, and your new lease starts the next day, and you negotiate a day of overlap. And you sure as heck don't want to be paying rent on two places for a month.