Why not unlock myth and BC now?

[Nekodar]

Well in 3 weeks time you will know. Basically it is not unlikely. And WP, AK etc are already at "useless" stage if you'd like to call it - literally something people just run for quick myths or just for relic quest. Do people farm Primal HM for weapons these days? Nope because you have Primal EX weapons already.

There are plenty of people that still haven't gotten any Primal EX weapon...

While people may not announce Primal HM farm runs much in the PF these days, they still happen.
Thornmarch in particular is fairly common as it's fairly easy and provides i75 weapons for people that want better weapon before they take on Titan HM for yet another relic quest.

Not everyone are capable of clearing the Extremes, and among those not everyone can afford to pay their way through...

While it will be easier to gear up to 90 from 2.2, most people are still going to go through gradual gear upgrades until they have one job/class equipped well enough that they can use that to farm gear for the other jobs they level.