As quoted above from theymos' post. Using coinjoin requires you 0.1BTC as the minimum amount.
Many doesn't hold that much amount.
Wasabi Wallet requires that, but others don't. Samourai Wallet's Whirlpool only requires a 0.01005 BTC minimum to access its 0.01 BTC pool.
Its privacy guarantees aren't as good as Wasabi, though.
Another great information. Thanks.
I'll check and see this whirlpool from Samourai.