Hello and welcome to this forum!
Yes, I often wonder why people buy so much from ebay, especially car parts that can be got from main dealers as the main dealer will be selling the latest version.
Having said that, some optional extras, ie accessories, seem to only get sold on ebay, by that I mean some accessories that were a sales failure - and you never knew about, were all returned to VAG main warehouses with only the local stocks being auctioned off and ending up on ebay. One accessory I did buy on ebay was "lane changer module for a VW Passat" - they turned up on ebay for £38 - and I bought and fitted it, then someone quoted that main dealers could order that kit in for £28 - but if I had never seen it for sale on ebay I would not have known that it existed!