True, theres no sense on having multiple wallets when you have only a small amount of bitcoin. Multiple wallets would be only ideal if you posses huge or large amounts so that you could able to partition it to lessen the risk of being complete broke when one wallet have a problem.
Yeah if you have small amount of coins then its good to go with a single wallet instead of going with multiple wallets as there is a chance that you may forget password in having multiple wallets.
Exactly small amount don't need a multiple wallet, but mostly members have a lot of amount of bitcoins, so that's why they refer to multiple wallets. Also i don't think that forget password doesn't matter, because now in that time, we have a a lot of work doing in laptop and i think all our accounts, and files have a password. So if we have multiple wallets, so forget password it doesn't happen.