Do you really think no one ever thought of using a steel gear before?  While at first the steel gear may seem stronger than the plastic gear.  Read on, you might be surprised at what you find out.

DiSEqC motors originally had steel gears.  But manufactures soon learned that steel gearing would not last for several reasons.  I have listed some of the reasons in the table below.  Motors with steel main gears are cheaper to make and still sold in countries where price is just about the only consideration.  In areas where a reasonable warranty period is expected, you will only find plastic gears.

"Plastic" is really a poor term for the main gears used in most modern motors.  The material is actually a high tech engineering nylon.  For this application it's stronger than steel and will last much longer than steel.  

Description	Plastic	Steel	Notes
Absorbs backlash shock caused from starting and stopping	Yes	No	Plastic gears have that slight amount of give required to absorb the shock of starting and stopping and from wind resistance.
Wear factor	Low	High	Plastic gears wear less.  Take a look at garage door openers and just about any other device that has daily use.  You will find they use plastic gearing.
Mechanic stop	Yes	No	Plastic gear teeth stop at the end of the travel range Steel gears have teeth all around and provide no mechanical stop
Requires frequent backlash adjustment	No	Yes	Steel requires adjustment more often then plastic because of it's high wear factor

Check the motors on the market.  You'll find that only one Italian manufacture uses a steel gear and they use a elaborate spring system to try to absorb the start stop shock.  They still suffer from backlash problems that develop shortly after putting their motors in service part of which is caused by the high wear factor even though they use hardened teeth in their gears.

So don't be so quick to believe "new and improved" when it's actually very old, outdated, and rarely used.  If it worked well, every manufacture would be doing it because it is cheaper.