To me they fun to build. That is what this hobby is all about.
I build a large range of models from highly detailed to whimsical.
Also if you look at some of the "cartoon builds" there are some that have alot of scratchbuilding to get the look right. I enjoy watching these builds come together as much as the highly detailed projects that have been posted.
Also to the question of whether or not serious subjects were put on the back burner for the cartoon kits that may be the case but also how many modelers got started with these kits.
Finally build what you enjoy and have fun along the way.
bobthehobbyguy