I'm not sure i have the answer to this, but I think gliding is a bit like alcohol (and no, I don't mean addictive, though Mary may differ!). If it was invented now, it wouldn't be allowed - or at least a lot of the things we accept because they've always happened, like gliders in cloud without complying with IFR, and massive multiple launches without proper NOTAMs (I.e. without a NOTAM which is specific about the location, numbers, routes) wouldn't be. Gliders are even allowed in class A airspace with prior agreement, where I am most definitely not welcome without an IR.
I do understand the difficulty of specifying the task until the wx is known, but I am also baffled by the use of discrete frequencies. Why on earth wouldn't gliders entering cloud above Lasham announce this to Farnborough? It's as though the assumption is the only other people around are other gliders. Farnborough were blissfully unaware that the day's task had been abandoned and were clearly only going from the NOTAM, information they and I had before I took off.
Tim