Why can't/won't Bungie bring y1 raids up to current LL?

Players are dropping from Destiny like flies. I hardly see 3+ friends playing at the same time. Whereas 3 months ago I'd have 15+ friends online playing Destiny.

Regardless of the current player-base, I've always wondered why Bungie doesn't just bring the VoG and Crotas' End up to current light levels? I'd kill for a chance to grind for VoG weapons, all of them! Same with Crota's rewards. That would give current/past players a reason to stay/come back and give the new players a ton of extra content.

I miss he elemental burns. However, I miss content and VoG weapons even more and would be almost as happy with a non burn version of the VoG weapons.

Bungie brought PoE back to the current light last year, why can't they do the same for y1 raids?

edit: I don't intend to imply that it's a simple task, I'm just curious as to why they haven't or won't.

edit: The player base dwindling comment was not meant to be snarky but more of a reason to update the y1 raids.