Keep it simple:
Pitch attitude IS speed control: 
On a glider you adjust your speed with your pitch attitude.
On a 747 without any thrust you have a veeery big glider
. Again you adjust your speed with your pitch attitude.
(Altitude is "just" a time factor
)
The bonus by power/thrust: You are now able to maintain your altitude - even climb (in most situations
)
So power/thrust IS altitude control!!!
By the way - ain't we just a little of topic??
