Consider this pattern:
In C Major:
And transposed to F# Major:
Pianists may notice it’s much easier to play this in F# Major. It fits under the hand nicely. It’s more awkward in C Major.
Here’s another example:
In C Major:
And in Db Major:
There are a few reasons why we avoid playing in difficult keys:
One reason is because the standard repertoire avoids them too. How many tunes did Charlie Parker write in B Major? As a result, when we learn these tunes and lift solos, we get comfortable interacting with the most familiar keys.
Another reason is because it’s physically more difficult to play in unfamiliar keys (at least for pianists). Maybe that’s why there are so few tunes written in unfamiliar keys in the first place! Regardless, we should take this into consideration when we’re practicing difficult keys. For example, if you want to improve in F# Major, I wouldn’t recommend that you transpose every tune and lick from F Major and expect to play them fluently.
Instead, I would experiment with a few selected licks that work more naturally (or are designed to work more naturally) in F# Major. Once you establish a foundation of licks with fingerings that fit under the hand, design some more, expand on them and experiment!
Here are a few examples that I derived from the lick above. With the proper fingering, your right-hand should glide right over them!