The blaster in the extender is more meant for mass close-range use, such as use in an equipment closet. Due to this, if the emitters were TOO powerful they would overwhelm more sensitive devices.

And, on the other hand, some devices have horrible IR receivers in terms of off-angle or distance performance. For instance there's something called "tunnel vision" where the IR sensor on a device is placed on a circuit board far back into the chassis and ends up looking down a long tunnel to the outside world. The further back it's placed, the less off-angle range and overall sensitivity it has. I seem to recall a few years ago some company selling stick-on IR collectors designed to redirect off angle IR in such cases.

Also, look in the manual - it recommends that the blaster be placed no more than 16 feet horizontally or vertically from your components, while the remote itself is rated to operate from 30+ feet. Also note that the blaster has emitters pointing out the TOP - which means if the blaster is sitting on top of a bookcase as you say it is, you should really trying having it upside down and hanging out a bit.

Otherwise, it was really meant to be used with the stick-on emitters.