Beast Machines was stale, with about 30 toys released in the year, and shelfwarming for years afterward. The last 4 years of the new Movies is definitely the opposite of stale. It might be the same main characters and forms for the last few years, boring many fans, but Hasbro profits (and Transformers being their largest earner for the last 5 years) would give them no reason to change anything.
Beast Machines was not a (money) winning formula, so they changed their direction, axing the line and cancelling Transtech... bringing in Vehicles from the JP Car Robots line.
Movie Universe on the other hand, is a (money) winning formula... and what business that wants to stay in business is going to change, or walk away from a winning formula.
We certainly aren't their meal ticket, so they're just gonna keep producing product for the kiddies and parents who are, no matter how repetitious it is.