Because if it tanks, it will likely go to -10% instantly, making it really hard to sell. The thing about price restrictions is that you can never be sure what the real market price is because no one has the information, especially in a bubble.

Most of the volume happens around market opening, because at that time no one is sure whether the stock will end the +10% strike that day.

If you want to sell at an all-time-high, you would have to risk losing out to sell at one of the +10% days.