I have been looking at a variety of RF transistor amplifier
schematics including a 50 watt amp shown in the ARRL handbook (1996 -
page 17.96) , and they do not have emitter stabilizing resistors and
ac by-pass capacitors on the emitter leg of the final output
transistors. Is there a good reason for not using emitter stabilizing
resistors and ac by-pass capacitors in 100 watt output or more RF
transistor amplifiers?

Here are some on-line schematics I found of high power RF power
transistor amplifiers, and in all of them the emitter goes straight to
ground.

http://www.ameritron.com/man/pdf/ALS-500M.pdf

http://www.cbtricks.com/Amp/txstar/2...350hdv_sch.gif

http://www.cbtricks.com/Amp/palomar/...r_elite500.pdf