I don't think that's the problem. I think it's mostly because it still has way less people (easier to mod), and also it doesn't show user karma, so there's no incentive to karma farm.
Higher reputation reddit accounts are sold and used to marketers for shilling. Old accounts with lots of karma fetch a higher price. Some ppl just farm karma for their egos.
It makes an account look authentic, which makes recommendations that account offers more genuine. E.g. advertising, political astroturfing.
There's so much of that on Reddit with accounts that look real but aren't. When I started using reddit (like 15 years ago) I was legitimately able to trust most recommendations (I still own and use many of the products I picked up and consider them good decisions), but it's been at least 7 or 8 years where you absolutely can't.