When you create an Electrum wallet, you're given by default twelve mnemonic recovery words which need to be re-entered to confirm you have backed them up. Only few people with photographic memory would be able to re-enter the recovery words without prior writing them down.
So where's your mnemonic recovery words backup? You very likely had to write the recovery words to some piece of paper. Did you misplace it, did you make a screenshot or any other wrong-doing with it?
All wallets have a confirmation step on mnemonic seed words for users. I am quite sure that most of users will do either write down these words or screenshot, then they can type these words correctly in a confirmation step, before using that wallet.
They maybe did not understand importance of wallet back up so, after that step, they did not store that back up safely and carefully and they lost it somehow later.
Some wallets even don't allow users to make a screenshot with mnemonic seed words displayed on screen. For example, with Electrum wallet, you can screenshot mnemonic seed words on computer but on mobile, you can not do it. If you try to screenshot, you will see "Couldn't capture screenshot". Then there will be only one choice left, typing wallet mnemonic seed words.
You can take a photo by your phone but it's not recommended too. Storing wallet mnemonic seed backup online, one phone is not recommended too.
