Deposit charged on middle of stay?

This has bugged me for a while now. Nearly a year ago I stayed at a Mainstay hotel in FL. Booked directly through choice hotels app. Upon checking in I fully expected them to ask for the credit card that I used to book for the security deposit. They never asked for it and never said anything about a security deposit. Checked in Monday night. Then on Wednesday night I noticed a "pending" charge on my card that wasn't there before that night. There is nothing in this hotel that you can charge to the room. Turns out it was the security deposit. So what's up with that? We stayed till Saturday for 5 nights total. Do some place now only charge a security deposit if they "think your up to something"? We like to leave DND on for the whole stay because our PlayStation and laptop doesn't fit in the tiny safes.