Well, there's still a cost to use it (it's not a free +2 all the time), and if you go for strict optimization, you're going to be missing out on using it elsewhere.
Honestly, Experiences are almost exactly like Fate's Aspects, so it's probably a good idea to read things like
What Makes A Good Aspect.
Not a bad idea, but "exactly like" is a gross overstatement and oversimplification.
First, there is the range issue either can be invoked for +2... but on DH, that's on a 2⋯24 range being affected, while in Fate, it's either a -4 to +4, or -5 to +5. (There are flavors with 2d6-7, others with other methods of getting -5 to +5. So that's 22, vs 8 or 10. Less than half as effective mathematically.
Further, Experiences lack the Declaration use and Compel use.
A large part of making a good Aspect is the Compel uses; irrelevant to DH as written.
Declaration would make sense, but it's not provided for in DH as written, tho' justifying a narration by mention of an experience is readily within the scope of the best practices.
A few Fate flavors also allow an Impair use - turning an aspect against the user. This differs from a compel in method and magnitude.
The best Fate Aspects aim for all three/four uses; often, the bonus use is secondary to the compel.
Other similar mechanics:
Aspects in
Houses of the Blooded and
Blood & Honor. These are a bit stricter than Fate Aspects, drawing them from the same source
2d20: Traits in
Star Trek Adventures and
Dune - depending upon the action and their relevance one of: +1, -1, allow, prohibit. (also in several others. Omitted in Fallout for some reason.)
BIGs in
Mouse Guard. Hinder for one turn in the player phase, or use for a bonus now.
Cortex Plus/
Cortex Prime have Distinctions: one's free to add. Can either add a d8 (helping) or d4 (risks hindering)
Features in FFG's
End of the World series of RPGs.
The thing is, any of these can provide good advice, but in all of them, except DH, there's a negative use to them, too.