Because they believe it is in their interests. They've done deals with Evri and Royal Mail so will be making some sort of commission on the services they sell. It also forces people to use tracked services, which e-Bay have long recommended, which makes adjudicating Non-Delivery cases easier.
For Sellers we only have to deal with one web-site, rather than e-Bay plus a courier/Royal Mail. e-Bay base the price on their estimate of the cost, which is as likely to be too low as too high, and honour that price. They also cover items against loss and damage up to £750.
We all have to decide if e-Bay is suitable for our needs or not and use it if so or don't if not.
Cacas vendit.
