Why may i use PVE gear in a pvp scenary?

I am raiding as bard and i do pvp as marauder, i haven't pve gear in marauder job.
May i spend soldier tomestone to buy a pve gear which i will not use in a high end encounter?
May i start to loot high allagan gear over my partners?
Why i am force to do pve to play pvp?
Why may i change my pvp job for another?

It's ridiculous.