Three things.
First, as someone who has never visited Thailand before, counting on an extension or a border bounce seems risky (to me). Many in the forum mention these items as if they are nothing, and they may very well be. I was just looking to do the approach that provided the least amount of hassle, once I had entered Thailand. This may be one of those things that once I have done it, it is such an easy process that it becomes a no-brainer. But for someone who has spent a frustrating day or two at the DMV in the US, the idea of trying to navigate a foreign bureaucracy in a language I don't speak, while in the middle of my vacation, sounds problematic.
Second, currently I have both flight and hotel reservations for 90 days. Immigration probably won't care if I have a hotel reservation for the full 90 days, but they might cause issues if my outbound flight is longer than the initial amount of time I am allowed to stay in the country. Not saying that they would, but since entry is often at the "sole discretion of the officer", I was not looking for anything which would cause the officer to deny my entry. (Someone above mentioned the Onward Ticket option, which is something that I might consider.)
Finally, as I understand it, That immigration requirements change all the time. Up until September, I believe that they were offering 60 days when you arrived, but then that suddenly changed. And I believe that the 45-day stay itself is a modification of a policy which used to be 30 days. Whereas with a visa, it is "locked in".