DH occasionally buys on eBay when he can't find a specific craft item he needs for his hobbies.
I bought a couple of small things to try it out. Wasn't impressed enough by the experience to wean me away from Amazon Prime.
I'm not eBay's target customer. I don't buy tchotchkes. I wouldn't buy furniture, since I rarely do and when I have, I have very specific requirements (small house, contemporary decor). I don't wear jewelry, and am no longer interested in fashionable clothes (been there, done the dry cleaning, not interested).
I value my time, and loathe going into stores, so Amazon's one-click order gets A LOT of my business. I'm brand-specific; after six decades I know what I like and what I don't. I haven't walked into a drug store in years.
I appreciate value but cost is not my primary concern.
Our biggest expenditures revolve around food: both dining out and cooking at home. We travel around our area by car, and fit in as many restaurants as we can manage. We've done two trips already this month, taking advantage of cold but sunny weather, no rain in sight. That was ten restaurants right there, six new-to-us places and four we had visited once before but wanted to try again.
Christmas is going to be a family potluck. Rather than deal with traffic and crowds I had the groceries delivered from two markets, easy-peasy.
eBay is not going to make any of that simpler or more convenient for me, so I have no use for it.