Side chains are centralized I.O.U.s that still need bitcoin transactions in order to be fulfilled. They remove the benefits of using the decentralized bitcoin

Side chains are centralized I.O.U.s that still need bitcoin transactions in order to be fulfilled. They remove the benefits of using the decentralized bitcoin network while still using the network. If 10 m people used side chains (just for today), it would take some of their transactions up to 40 days to fulfill. If 10 m used it again (just tomorrow), it would take almost 3 months for some transactions to fulfill. Most merchants will not wait that long for an I.O.U., especially with fluctuating BTC exchange rates, making side chains much worse and less competitive than ACH.