It is about proportion

In the UK CAT generally flies in controlled airspace, gliders do not.

Gliders do occasionally fly in class D airspace where they are
'controlled' by ATC and are therefore 'known'

Gliders do occasionally fly in class C airspace in clearly defined wave
boxes or TRAGs.

For the last 60 years gliders have crashed into gliders but not into CAT.
There has been one occasion when power flew into a circling glider but I
guess he was looking at his instruments (or adjusting his mode S?).

The reason the suits want to mandate transponders is so that they can
allow their CAT friends (and backers) to fly more in class G airspace
without the need for lengthy and costly acrimonious consultations on
increased reserved airspace.

The likelihood of a CAT on glider mid air remains low if CAT stay
controlled and gliders stay out of controlled airspace. With a reduction
in CAT due to economic and fuel woes as well as environmental pressure
means we do have time to develop an effective low cost low power
alternative to Mode S. Perhaps 60 years.

Jim

ps: how do you put a transponder in a Hutter? or a paraglider?