The plural of toast is toast (“I eat toast” can mean one slice of toast or many slices of toast). It makes perfect sense that you put an “s” on the end - I don’t know why we don’t, I think it’s just an irregular plural 😁

Toast is used for singular and plural in English. If it is liquid, we'll always say drink instead of eat. 😁 I'm also a big fan of toast and jam.