Since sidefx labs tools are so useful nowdays,why not making them embed with houdini?Or at least make the labs option default checked on when you install houdini.So finally the render farm won't tell me i'm lacking the labs nodes.

If they were included by default, then they wouldn't be 'labs' tools. They're experiments that may or may not pan out. Some of the tools that are good make it into the main version of Houdini eventually.

Labs are split from Houdini to allow development that is separate from update cycle of Houdini. New features in Houdini in general are released on full or half version release. Labs are updated constantly and often by outside contributors. Irrc some version of labs is installed by default for Houdini 18.5+.

Is the farm in-house or is it rented? In case of in-house one it's quite easy to setup env variable that will take care of that.