My hunch is it has to do with the opportunity cost of investors. If a startup comes to an investor with a 1.1:1 ratio why would a rational investor invest? They can get that rate of return in less risky asset classes.

As a bootstrapper yes a lower LTV:CAC ratio could in theory be fine. But I would think like an investor. Instead of investing money you are investing your time. It would be better to iterate and tune what you're doing until you're getting a higher return on your time than you would working in a corporate job you could get or, if you do have capital, a higher return than you would get investing in less risky asset classes.

To your point, time to recover CAC is extremely important to bootstrappers. I recommending going after a niche in your market that can afford higher ticket pricing and will jump at annual deals in exchange for (say a 2 month) discount so that CAC is recovered in month 1. This is very doable but requires sales skills which many technical founders don't have. But they are very capable of mastering.