Offensive holding discussion

Does anyone else wonder why a call that is subjective goes for a ten yard penalty? I saw a stat on the saints d that says they allow a Lil over 6 yards per play the worst since the 30's or something like that.If the worst D of all time will only give up six yards per play how crippling is first and 20?This is how I think the NFL is controlling the flow not the outcomes of primetime games.It should be no more than 5 yards like offsides.And why do they let the play continue if its all for not?Blow it dead, hate to see players wasting effort.

Googling around had this explanation, which i guess makes sense for most teams on first blush.

Holding happens most often as an attempt to avoid a sack. A sack could reasonably be seen as a loss of about 5 yards. So the other team gets the 5 yards they should have had in the sack plus 5 yards as a penalty.

Though for the Hawks it seems to often run or pass.