I don't know why you assume that A) the only thing you can do with skills is drop a bonus on them, and B) that the only thing that is useful out of combat is a skill.
I don't assume that. I just have seen in 4E how many utility powers affect skills and how strongly they affect them, and do not think that the 5E designers will do anything better.
For example, search for the word Diplomacy in the powers list for utility powers.
Arcane Mutterings: Arcana check in place of the Bluff, Diplomacy, or Intimidate
Suggestion: Use Arcana instead of Diplomacy
Where is the balance here? Both of these average probably +7 or more to the roll, but one affects one of three skills and one affects a single skill.
Waukeen's Silver Tongue: Reroll Bluff, Diplomacy, or Intimidate with +5 bonus
This power is effectively a +8 to the skill because it will only be used if the skill check is failed. Being able to have someone get an effective +8 to one of three skills every single skill challenge is, IMO, seriously unbalanced. Especially when one considers that the user of such a skill power probably has pretty strong numbers in one or more of these skills to begin with.
I just think that based on track record that WotC will just go crazy with the utility portion of powers, especially for ones they use for skill adjustment.
In fact, I wouldn't be surprised if they didn't try something like: the attack portion of this power is lame, so let's combine it with a utility power that is kick butt.
I also think that if they combine attack powers with utility powers, that the number of powers won't decrease that much since they will still want to fill up levels with the same or a similar number of powers. That means that the game might become even more complex when instead of there being 10 attack and 7 utility powers, there might still be 17 powers that are 17 attack/utility powers. It's fairly difficult for some players to keep up with all of the powers as is at late heroic or so onwards.