I invite everyone to a reasonable discussion about this topic.
There is a new topic about it on the eu forums as well. Some of the reasons behind this can be:
-A person that sees the new pvp transmogs at the launch of the season and really like them, but never played pvp, that person will never be able to get them, since he cannot build enough experience in 1 season because the time is too short.
-A person that didn't play for a while, starts playing again and he played some pvp in the past and decides to start playing seriously, but he started at the middle or near the end of the season and has no time to gain them.
-A person that is almost similar to the previous one, has casualy played pve and now wants to play pvp and during 1 entire freaking season, he wasn't able to find the right partners to do this with.
-There shouldn't be any reason to be honest, since their pve counter parts are still obtainable anytime after the current tier becomes irrelevant.
https://eu.battle.net/forums/en/wow/topic/17615233423