On Sunday, May 5, 2019 at 7:23:36 AM UTC-7, wrote:

One prejudice could be that an experimental glider should not be used by commercial operators...

That's not prejudice, that's the law spelled out in 14CFR. Aircraft without standard airworthiness certificates can be used for commercial operations only under certain narrowly-defined circumstances.

...or club training/casual use.

That's a bit murkier. Depending on the structure of the club, it may be possible to make experimental aircraft available for club member use. But it's usually not worth the trouble.

--Bob K.