Vanilla and Non-Tek servers will attract people from Legacy Vanilla servers. Primitive+ will attract mostly Prim+ and a few Vanilla and Regular Primitive players during the first few days. Meanwhile, the majority of the Regular Primitive demographic has no new servers to attract them. Basically, they have nowhere to go that is similar to their current niche.
I agree that Non-Tek does NOT need PvE servers - they will still have access to all their tools on a Vanilla PvE server, they can just choose not to use the TEK stuff. Prim+, however, does have a bigger need for it, as some of the stuff on there is unique - it cannot be found on neither Vanilla nor Non-Tek.
WildCard could drop the PvE Non-Tek servers and turn them into Regular Primitive servers. But they already promised to make those PvE servers, so it wouldn't look too good - and their reputation might already have taken enough damage recently for them to not want to harm it further.