Another mystery just like how Roland Garros and Wimbledon don't invest in some lights so that players can see something when matches go on at 9 pm.
As for Roland Garros, I'm not sure if it is such a negative thing that they don't have lights because clay and floodlights usually don't get along too well in terms of good sight. Well, for some it's an enormous problems, for some less. But it's much more problematic than on hardcourts.
Anyone know why we very rarely have indoor red clay events? I remember a Futures or two being played on it but that's it.
It's possible of course, but mostly such temporary indoor clay courts which are laid in multifunctional arenas or domes are of a worse quality because a good claycourts needs to be set well in advance and consists of more layers than most of these indoor clay courts which are typically used for Davis Cup, for example.