It's been suggested before, in various forms, such as: Making invitations equal to total number. Differentiating between invited and accepted, and returning the right to invite, whenever an invited player leaves or is kicked. An extra invitation right as a reward, for instance in GE.
I suspect that the idea behind the limitation is to prevent FLs from becoming closed circles of players, (almost) exclusively friended to each other, with (almost) no outsiders, as well as "forcing" established players to accept invites from new players, simply because they can't send invites themselves. If I'm right, Inno will be very reluctant to change it, without both a good reason, and confidence that the problems can be avoided in spite of any changes.
The reward model, with some few extra invites, scattered over extended periods, probably wouldn't do any harm, that I can see. I'm also fairly sure that it would become a popular feature. It probably couldn't be common enough to serve the purpose at issue here, though. Whether Inno hasn't picked up on the suggestion, or simply disagrees with it, or have concluded that it's too much work for too little profit, or are working on it as we speak, or something else altogether, I have no idea.
BTW, if anyone steals my booze, they'd better focus on their defences, rather than waste time on pleasantries!