I said motifs are repeated. Tropes. You can apply it to the most trivial up to the most important.
The Empire always build a superweapon
All people on Tatooine are moist farmers
All Protocol Droids are prancy
All correlians are good pilots
Bothans are spy
Etc.. etc.. the writers of the EU just wanted to recreate the stories and elements of the original movies. Everything seen there became an overall generic trait in their world building.
Except Zhan. Or Stackpole. You know, the non-hack writers.