Most of those "free coins" are dead/shit coins. At first you'll get excited because you got it for free and big amount but when you look at the price of it. It's just worthless or can't even go higher that 1 sat. Yes, you can collect all of them but the main question is "is it worth the time??" Of course NO.
Yobit made that for their marketing strategy to make newbie users come back and get another "free coins" in the next 24hrs. (wise but terrible support)