Well if they ever upgrade the GC catalog there would be more reason to farm the seals. The thing is though I use mine for pretty much only Ventures, and I'm usually swimming in seals as it is because the dungeon gear from high levels gives around 1k seals for a trade in.

And no I've never suggested it (though I suppose I just did). People want the tomestones because of how the game's progression system works. You need them to move up. So people want the fastest way to attain them, and Low Level isn't it.