Why do so many people oppose expanding Bitcoin's use cases?

Genuine question.

Whenever new Bitcoin use cases are discussed, whether it's DeFi, lending, staking, or other applications, there's always a group that strongly pushes back against them.

If these developments are optional and don't alter Bitcoin's core properties, why the resistance? Is it mainly about preserving security and simplicity, or is there a concern that additional layers eventually introduce trade-offs that could undermine what makes Bitcoin valuable in the first place?

I think healthy skepticism is important. Not every use case deserves adoption. But if people are free to opt in or ignore them, shouldn't the market decide what provides value?

Curious to hear different perspectives.