In game i usually run a 4 pokemon team, and two hm slaves and dont worry about natures and ivs and evs
Amen.
I always just play through making sure to do the following:
-Examine every house
-Talk to every person
-Catch as many Pokemon as possible
-Raise a full team of Pokemon (screw that 1-3 bullshit. I play like a fucking man!)
-Don't give a shit about natures
That's how I played as a kid, and as they say, "Kids do the damned best things".
It's definitely a glitch if you look at how it happens:
IVs are stored like this in binary:
00000|00000|00000|00000|00000|00000
These are Sp.Def, Sp.Atk, Speed, Defense, Attack, and HP.
So IVs of 31/30/29/28/27/26 (Sp.Def last) would be stored as:
11010|11011|11100|11101|11110|11111
Normally, when you catch a Pokemon, data for its IVs is copied from the "wild" data slot to the "box/party" data slot.
However, on a roaming Pokemon, the copying messes up, copying only the last eight bits instead of all 30 of them. The uncopied bits are all set to zero.
So the 31/30/29/28/27/26 example changes from:
11010|11011|11100|11101|11110|11111
to
00000|00000|00000|00000|00110|11111
or 31/6/0/0/0/0. Ouch.
(And this glitch occurs in Ru/Sa and FR/LG, but not Emerald).
(Random trivia: A glitched wild roamer has a 1/256 chance of having all zero IVs. lol)