Regarding the first question, I have been burned before by non-technical co-founders who turned the project into their own little "I want to learn how to program" experiment, while spending zero to no time actually hustling, talking to people, getting feedback, finding more early adopters, engineering requirements and so on. I have learned to be a better judge of character through that experience, and am much pickier now.
About the second one, I was actually paraphrasing something I heard Max Levchin state at one of his talks years ago. Not sure how much it's worth, given his partnership with Thiel.
I have another possible explanation for that first question, and I am making the assumption that I'm not the only person that has had to work on not feeling this way:
Even though we really shouldn't feel this way, a lot of us developer sorts wrestle with the idea that we're the only ones ever really working, specifically in the pure development phase of a project.
Granted, I'm sure everybody feels that way at least once during a given venture. I've forced myself to stop thinking that way, but it seems a fairly human thing to think.
Already said (far) below in this post, but the work on the part of the technical team to produce an MVP is often front-loaded, which means that the technical person (team) assumes most of the initial execution risk. Equity distribution should recognize the assumed risk.
If the technical person does not execute on the MVP, the idea guy mostly out only lost time-to-market. On the other hand, if the technical person delivers, he/she is now "all-in" before the idea person typically contributes meaningful execution-value towards the business.
Its probably most fair to view the first "execution" contributors (technical team building MVP) as the first investors in the business, and therefore should be recognized with more favorable terms (equity distribution). If the idea person can create actual execution value in tandem with the MVP, then an initial 50/50 split is fair.
If you have an "idea" person, you're screwed. You need a product person. I don't know how to code, but I can help with wireframes, customer interviews, feedback, marketing plans, pricing strategies, partnership opportunities, etc. The very idea of an "Idea Person" needs to go away and people need to be accountable to providing value. And you don't need an MVP for the Product Person to start working. And I use that term very loosely. Because if they aren't building the product, they should be supporting/defining/selling it.
About the second one, I was actually paraphrasing something I heard Max Levchin state at one of his talks years ago. Not sure how much it's worth, given his partnership with Thiel.