Why are recreational glider cockpits so small? If someone built a glider with a 25% larger cockpit, would it hurt the L/D that much?

Are all high performance gliders built for racing and by consequence make the sport unattractive for larger people?

How many people retire from gliding because they no longer fit in their gliders? How many never try the sport because they find the cockpit claustrophobic and uncomfortable? How many teenagers solo only to grow too big to fit in a glider?

If Eastern Europeans grow larger over time, will glider cockpits get bigger?

If the sport offered an extra large cockpit, would it increase participation levels?

Has anyone modified a two place glider to accommodate an extra large pilot?