Most mash schedules can be completed in about an hour. Basically yes, there's other stuff going on in longer mashs.
A step mash to hit a protein rest, beta-amylase, alpha-amylase, mash out can easily take a couple hours depending on how quickly your system can heat the mash. Also, if your water grist ratio is too thin, it could take a long time for conversion. A coarse grind will also benefit from a longer mash time to extract starches from the larger endosperm chunks.
Ultimately your mash is done when all starches are converted, unless you want to manipulate proteins or produce other flavor profiles like clove by producing precursor compounds that can benefit the yeast for those esters.
If you just want a basic mash with a split of simple and complex sugars 152°F is good. I've done these mashs in as little as 20-30 minutes, confirming conversion is simple with an iodine test. So no time is wasted. Also it works very quickly because both enzymes beta and alpha are active even though beta amylase is being denatured at this temp it hangs on for about 30 minutes.