Because a conversation about communication is a lot more fun than another conversation about guns.
Personally, my breakdown would be "[49%..50%]: Almost a majority. [45%..49%): Somewhat close to a majority. [40%..45%) Not really close to a majority. <40%: Nowhere near a majority.:
15% is pretty much a straight minority. It means the VAST majority are opposed. That's going into "You should never use this number in the same sentence as 'Majority'" territory, imo. If you're more than 15% AWAY from a majority, you are nowhere near it. Just like how a 65% majority is nowhere near a minority, a 35% minority is nowhere near a majority.
At 30%, it means whatever metric you're using to track your majority status, 200% of that metric is opposed! o_o There's twice as many people against you! You are outnumbered 2-1. I would feel pretty darn safe calling that nowhere near a majority.
But we aren't dealing with "A" and "A's opposite, B", we're dealing with "A" "B" C" "D"...
For example, if we had a poll of, say, favourite bands, and it went something like 30%, 10%, 5%, 5%, 4%... then while 30% might not be the majority, it would be a significant plurality and wouldn't be described as "nowhere near" a majority. After all, if you have enough options on that list, that 30% might be so because there are people who are split between the 30% option and, say, a minor band getting 2%, so they aren't diametrically opposed. Similarly, when referring to the broad topic of "murder", what falls under "caused by drug war" and what doesn't isn't necessarily clear cut.