Sidechains breaks the single-point-of-failure problem which vexes a 'one-size-fits-all' solution and pushes the critical infrastructure support role to people who can handle it. It also pushes the benefits of a counter-party-risk free solution down to the masses. Nobody can stop the masses from giving their money to shysters but it's very possible to arrange for the sidechain operates themselves to have a tough time robbing their users (unlike general alts.)
The entire point of Bitcoin is to push the critical infrastructure support role to a decentralize DAC that no people handle or control and that has no single point of failure.
Your entire argument is contrary to the very purpose of Bitcoin and most people's participation in the project. If Bitcoin become becomes dependent on SCs that manage risk for people to protect them from their own mistakes, then we are back into FRN land, where we are all protected and coddled for the minor fee of being slowly boiled alive in the FEDs inflationary pot.