That's not as easy and convenient as it sounds. At least not if you aren't storing all of your holdings on a desktop or mobile wallet.
If one has a hardware wallet with multiple currencies, it would be a pain in the ass to completely move all funds out, setting up a new seed, moving all funds back in.
You will lose daily access to your old addresses (which might still be needed for signing messages). And you also have the problem of securely storing the coins while you are setting up a new seed.
If, for example, one is only storing his coins on a desktop wallet without many periodically transactions coming in, it is no hassle to change the seed and simply 'forget' about the old wallet/seed.
But for anyone who does need access to his old addresses for signing etc.. such a hassle simply is not worth the few bucks you gain with these forks.. especially nowadays..