Well, yes, and no
Flaps will improve the lift Coef of any wings, up to a certain point, then, generate more drag.
Same flaps up will increase the speed up to a certain point (you are destroying lift (?) ) good for transition for exemple, to get to one thermal to another.
So, flaps are good as they will increase your range of application, but you have to be carefull ! All profiles are not designed to have flaps.. You can add them, but the result might be worse than the remedy !
Some profiles are specifically made to have flaps, like some TP/SB for recent ones or Wortmann are made specifically to have flaps.
For a Wortmann for exemple, a serie FX xx xxxK /10 mean that the profile can have flaps (letter K), followed by the size of the flap ( size is 10% of the chord here)
And also pure lazyness ! Easier to build a wing without flaps ! :lol:
But maybe someone will have a better explanation! Based on experience, like for the Algebra, I put 1mm of flap (barely see it moving down!) and the thing keep going up, more, and that's it, the thing won't fly, just brake !