For the longest time I wasn't interested in the premades. Then Freetime released, I wanted to play in the new neighborhood, so I moved all the Desiderata Valley premades out of their nice homes and into barrack-like houses at the edge of town. While I slowly introduced my own sims over the next days, I felt bad about my decision, because it reflected a real life issue: The wealthy newcomers can afford the good houses, rent rises and the locals are forced to move to the outskirts and into grey concrete apartment blocks.
So I started playing the Desiderata sims, then the Bluewater sims and the downtownies along with my own characters. To this day mixing Maxis sims with my own is what keeps them interesting for me, because depending on who the same premades interact with, they will express different sides of themselves.
In Sims 4 I have a bunch of premades including sims from trailers that I love to pieces and have saved to my library to protect them from any lore or style rebrand. They may not always get played, but I love seeing them in the background in all of my saves. The vast majority, however, I either ignore or delete. One thing I noticed is that ever since Eco Lifestyle premades have it harder to win me over. I feel I already have a large and varied enough cast and so any newcomer has to stand out particularly well.