Their typical responses are (I'll paraphrase):

• They don't see it having a bright future like Eth or some other project.
• They feel tooling isn't as readily available to build cool projects.
• They think Bitcoin is only about the asset, no smart contracting or interesting things can be built on it.
• I can't build on a planet killer (due to PoW).
• There is no clear path for me to become a Bitcoin/LN dev (something Qala is solving).
• Some feel it is a scam (a small minority).

So I'd say I get several consistent responses when engaging with devs, usually falling into one of the many above.