Is there a reason someone would continuously send ETH back to itself? (through multiple wallets?)

I was looking at this large ETH wallet with more than 100k transactions out of curiosity and I noticed that it's using multiple other wallets to send money back to itself. It goes like this.

OriginalWallet>UnknownWallet1>UnknownWallet2>UnknownWallet3>OriginalWallet>Repeat

It's no small amounts either and it's doing it regularly. Is there a reason for that other than waste gas?