HSAs are only available alongside high deductible plans (HDHP), which aren't necessarily ideal in all situations. FSAs are the only option like that if you don't have an HDHP.
Surely, that is offset by having to forfeit or waste any FSA money not needed by the end of the year. It really only makes sense if you have a minimum amount of guaranteed healthcare expenses every year.
What is the point of having a low deductible when you could put the premium difference in a HSA and use it on either the deductible or something uncovered?
The math on whether you are ahead with the HSA or not is non trivial, especially if you are married and neither employer offers any subsidy when you put your spouse in your plan. HSAs are often better, but it's a very unfortunate math problem, where you carry quite a bit of risk. The HSA contributions from your employer are often nowhere near enough to make it win all the time. If your employer's does, consider yourself lucky. On any given open enrollment, my household has at least 30 combinations of healthcare plans to consider, and that's ignoring dentals, visions and the like
There are some cases where an HSA is unavailable. I've had an employer not offer a high deductible plan. I've had an employer offer a high deductible plan, but the insurer not supply it in my home state.
There are cases where it doesn't make fiscal sense. One employer covered 1x premium/employee(spouses and kids were full rate).
