Imagine this scenario.
A gliding competition in southern England with 100+ gliders all with
transponders, Plus non competition gliders flying with transponders, Plus light
aircraft flying VFR, Plus commercial, Plus military all with transponders
bleeping away.

The poor chap on the Radar would have a totally confused picture. The
authorities would then want to make sense of it because they look so close
together on the screen, all these people flying VFR outside controlled
airspace.

Before we know where we are there will be NO uncontrolled airspace and since
gliders cannot maintain nice neat constant heights and headings they would be
banned.
Paranoid me? Maybe