I suspect a lot of people asking for level 31+ for VoG started playing after the Crota raid came out so have far fewer VoG than Crota completions. They got used to Crota first, which is fast (and easy, glitches aside) and want a similar experience in VoG. For me, the fun of VoG is it's a challenge and requires a good team who can communicate. It takes an hour on a clean-ish run (realistically, obviously we've all done it faster than that). Compared to 35-40 minutes for Crota hard. Personally I steer clear of those groups. I joined one at Atheon once and the leader looked at my gear, complained I was using a 300 weapon (Vision of Confluence) and asked why I switched from Ghorn to SGA. He threatened to kick me, so I just left and found another group. If I ever had a weekend to kill, I'd be up for putting my VoG gear on getting a team of like minded people, and challenging a 'L31+ only' group to who finished the entire raid fastest, 'level 31+ only' or level 30s with 300 attack. I'd put good money on finishing it significantly faster than the 'L31+ only'ers.