There are some public policies that need incentives to go against the market, because market forces are not inherently good.
Sometimes there is a need to legally mandate something, or are you also against environmental protection laws? By this logic, f people really care about the environment, would it solve itself then?
Importantly, to pick just one of the reasons, you can't expect users to accurately judge complex technological product, especially when facing marketers who will lie to them. When you're shopping for food or medicine, you're not expected to understand biochemistry or technicalities of randomized control trials - you expect the things you buy to not poison you. Plenty of vendors would be happy to sell you literal poison - and they did, in the past - but we've regulated that possibility away. Similarly, for technology, some of the abuses need to be regulated away, because you can't expect regular people to avoid the traps, and the vendors to not be abusive without external pressure.
And just looking at exercise bikes, it's true that peloton/flywheel/etc are closed. But the products in that space from the established fitness tech players (eg wahoo and tacx) are entirely based around communicating via standard protocols (ant+ fe-c trainer control).