Nope, Mem usage cannot be the point, remember they did that old "S.A.M. reciter" text 2 speech on a C64 and it also ran on my ATARI 600XL when it only had 16KByte of RAM ...
And its Quality was good enough, i even think those "roboter voices" are far more amazing than a "perfect female voice" ( under *some* circumstances i have to admit :-) )

My 0.02 Euro ...


Nils

( If i dig deeper in the dark regions of my mind i also remember text2speech on the Radio Shack TRS-80 with 16KBate that my best freinds brother brought to our village, and that led all of us kiddies to be computer freaks, maybe majorly because of that thing actually *SPEAKING* , so *never* underestimate the facination of a computer speaking to non-techie people ( and that's what we were at the age of 8 ). )