In my first year PT class I would say roughly 80% of us worked as a PT aide at somepoint in the 1-3 years before coming to PT school.
You could interpret it two ways: First, that it's a highly valued position and something PT schools look for. Or, that it's such a common position that it's inevitable that a PT school class would have a lot of people with an aide history. I'm inclined to say it's the latter...75% of our class probably have worked a retail job during college as well, but that certainly wasn't required for acceptance, but it's just such a common thing. PT aide positions are not the same as retail, of course, but in pre-healthcare fields, it's a logical choice for people wanting exposure to the medical field and thus there are an abundance of applicants with that title.
A PT aide position won't hurt your application by any means. Nor is it required for applicants. Honestly, I think PT schools don't really care one way or another. In many PT aide positions the job is 75% changing linens and scheduling patients and not much hands-on work...in those cases, students who spent their time volunteering/shadowing and getting really solid patient work but weren't hired as an aide are better off from the PT preparedness standpoint. That's why on the application they like to see that there are a variety of experiences. For example, I had probably 900 hours at the time of application as an aide in a clinic, and then about 100 of observation in other settings. I don't think having 900 hours as an aide put me above someone with 200 hours as an aide, or behind someone with 2000 hours as an aide. At a certain point the number of hours stops mattering.
But after rereading your original question, here is my answer: the main benefit of working as an aide is the connections with a PT for LORs, the pay (although you'd likely get paid better doing something else), and exposure to the general feel of the field. The title really won't help you a whole lot, in my opinion. Someone with solid experience as an aide will likely have slightly better LORs because the PTs will undoubtedly know you better than when you only observe for 10 hours.