Lol, but try scoring a video or film, or orchestrating the philharmonic in GP, oh that's right, there isn't any video timeline and video screen and no orchestration.
Now you understand my "ack" when Sibelius was brought up in this thread.
The keypad in Sibelius is reserved for the note values, accidentals, ties, trills, all that kind of stuff. Quite frankly, though I am aware of it and know how to get to it, I am a note guy rather than a tab guy and with Sibelius there are a few ways to input notes. Since I am also a touch typist I use the note names to enter the notes on the qwerty keyboard. This way I use might right hand on the keypad to select note values and accidentals etc and my left hand to enter notes.
Guitar Pro, being a tab editor, comes up in input mode so you're ready to go right away. Sibelius, being used for a much wider amount of things, doesn't assume you're opening it to enter notes. There is a lot more things that can be done so it opens in select mode by default. It's up to me to decide what I want to do and select the mode that will get me there.
MuseScore is the same, you activate note input, it doesn't start by default. But, again, it is notation software for scoring and not a tab editor.
Edit:
fret number on my key pad.
I just tried the tab instrument and using the number keys at the top of the keyboard works the same way as the keypad in GP.
I use all three, depending on my goal, GP6, Sibelius, or MuseScore. Though these days I use a beatbox with Ableton Live more than any of them.
Eric