I guess that depends on how you interpret the stats, then. Is someone with Cha 8 significantly less charming than someone with Cha 10? Or is it negligible?
Using math as the guidelines, I treat someone a -1 as barely noticeable, since it's something that doesn't have an impact on anything, ninety-five percent of the time. It's only one time in twenty that the Cha 8 character will say something dumb and offend the NPC.
If you interpret the stats as much more meaningful than the math would suggest, then I can see the merit in taking a +1 to a bunch of stats that almost never come up.
I don't get why some people want to make more out of an ability score than it is.
A 6 Int doesn't mean anything more than a -2 on a d20 roll, having proficiency in the related skill puts you on par with a person with an 11. The d20 is a huge range, a 6 Int barbarian rolls Int (history) to see what he knows about an ancient dragon graveyard he gets an 18, the wizard with a 20 Int rolls Int (history) and gets a an 11 on the die, after modifiers for both have proficiency they get the same result.
The NPC doesn't treat you any different if you have a 4 Cha as long as you roll well.
Stats are only the modifiers, and if you want to multiclass you need a couple 13's, that is it.