That's probably the main reason. Plus many users probably don't want to lock their Bitcoins, which is capital, in channels where they can't be utilized for more incentives.
I heard that there's going to be a "Bitcoin DeFi" narrative that will come from Asia. If people who run Lightning nodes for incentives can't make 10% from their Bitcoins locked in Lightning, then I believe they might lock/stake them somewhere else.
I doubt that there is any kind of need to earn 10% on your bitcoin in order to be incentivized to lock them in a risk-free (and self-sovereign) way, so the BIG questions would be whether the BTC is locked in a risk free (and self-sovereign) way, and if that were to be the case, I would imagine anything above 3% would be incentivized to earn yield on the most pristine asset known to man.
Part of the reason that many of the various shitcoin Defi products offer such high returns is also based on a decent amount of risk including third party risk bu als that they are using shitty assets as their medium as well.
It definitely will not be without any risk, especially because it's unregulated with no F.D.I.C. assurance. Plus if I'm to do some shitcoinery with Bitcoin DeFi, I want, at the minimum, 20% to 30% yield for locking my Bitcoins for the purpose of liquidity provision, or lending. The risk of getting your coins hacked or stolen is simply too high.
Honestly, what use do we have for DeFi? I can't think of any, that can be implemented safely.
If we look at Ethereum's DeFi stuff, everything over there, all the yield and stuff, just mirrors traditional fiat banks. An ineffective and obsolete financial model.
But who is "we"? Unless you're very confident you're speaking for everyone, especially the Chinese miners who are probably ready to participate to unlock Bitcoin's potential as capital.