I own a good number of early texts, but not all of them, so this answer comes with a caveat, which is there may be some goals missing. I believe, however, that I’ve included most of them. These goals were culled from texts dated between the 11th and 15th centuries CE.
Pranayama was practiced for many reasons. It was supposed to lead to steadiness in preparation for meditation. It was also supposed to burn up karma (to then avoid re-birth) and sins (even for murder), counter disease and lead to a long life, and ultimately to self-liberation.
The controversial goal was power. Most modern teachers warn against the powers that are said to develop with yoga practice, deeming them dangerous distractions from the “path.” They do this mostly for two reasons. First, to avoid giving conservative Western religionists more ammunition against yoga, which to many of these folks is a Hindu in sheep’s clothing and so an invitation to “heathenism” and eternal damnation. Second, to avoid attracting “fringe” elements to the practice, hoping to acquire these powers for who knows what reasons, and so giving it a bad name.
Modern teachers don’t want a bunch of Anakin Skywalkers in their classes on the off chance one of them will end up as Darth Vadar. The fact is though that many old yoga practices were meant to develop these powers, and practitioners were frequently (though not always) encouraged to cultivate and refine them. What powers? Subtle sight (x-ray vision?), clairaudience, invisibility, and the ability to enter another’s body, just to name a few.