The requirements for brakes on pop-ups vary from state to state. Many to most require brakes on trailers of 1500 lbs max gross wt, others used to go as high as 3000 lbs. As a result, electric brakes were usually an option on the smallest, lightest pop-ups (8ft boxes). Dealers in states with 1500lb no brake limit would order them with brakes, dealers in states with a higher limit might not, depending on their customers. The 10ft boxes and bigger had/have electric brakes standard.
It's gotten a lot harder to buy a small pop-up without brakes because people travel to more states, states have gone to lower limits, and people are buying their pop-ups with more amenities like fridges, 12V and shore power systems, water tanks and sinks, heaters, etc, - all of which tend to drive the pop-up weight beyond 1500lbs.
Tow capacities of smaller SUVs have also grown - 3,500lbs being the normal tow capacity compared to 1500 - 2000lbs of 10 years ago.
2019 Flagstaff T21TBHW A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time