Because this is a game of vertical progression.
If you remove the carrot, what are you left with? The reward needs to justify the means to get it. Want the big boy pants weapons? You'd better do the big boy pants content.
Endless coil is an extreme but relevant example of this, my own group is very likely capable of clearing it, as is my previous group from Gordias/Midas, in both cases, motivation has been the key stumbling block with my current bunch being unwilling to even dip their toes.
Remove the desire for those Savage weapons and you'll do the same to a lot of casual/midcore groups, which will potentially lead to another big drop in raid content interaction rates amongst the player base as a whole (The very reason we've got these comparatively easy raids in the first place).
By comparison, relic weapons are a pure and simple time sink with very little challenge beyond 'Can you afford this mat?' or 'Can you stay awake?'. They are very different things and as such, offer very different rewards. I do think it'd be nice to have them attaining parity during odd numbered patches (aka mid content cycle) to spread content out a little tho.