Do you have confidence in yourself?
How many time do you change your wifi password per month? If you never change it, your neighbours is using you free wifi internet.
However, do you have confidence in your memory? Can you remember anything? I dont believe on my when I have 42 passwords to remember. Wifi Password Manager can help you, not only it can keep your wifi passwords but only keep every your passwords in secure.
Dont trust any online tools, your passwords only secure in your phone only!