I don't plan to ever buy complete series of Star Trek, but I have the Time Travel collection because I like time travel stories and it has some of my all time favourite episodes of Trek in it (and it's because I like time travel stories that some of those are my favourite episodes).

I find the Transformers sets unappealing though because I would be looking to buy complete seasons, but also because the grouping is based on a false assumption that it's the same character across series. G1 Bumblebee, Animated Bumblebee and Prime Bumblebee are all extremely different characters who only have a name and colour scheme in common.

The various Megatrons and Optimus Primes have more in common but are still very different, and pulling a random ep out of a series with a strong ongoing narrative (like the Unicron trilogy and Prime) surely makes them rather unintelligible.