The way I do it is as soon as I write down the Seed, I close the Wallet, then re launch it and use the Restore option. Enter the Seed from the paper I just wrote and go from there.
This is the practical solution, without need to worry if you mistakenly wrote the seed.
AFAIK most of wallets asking you to input the 12-24 words to confirm if you've save your seed phrase and they also give a warning message if seed phrase is really important and don't lose it. So I guess with a common sense, people nowadays won't lose their seeds.
What people need to pay attention is don't intentionally forget or delete your old wallet seeds, you or someone might unintentionally send coins to your old address.