I don't know, and the answer isn't clear. The general answer to this kind of question is because english wasn't invented by some person who made up consistent rules and patterns. Most likely the two words are from different languages which had different ways of forming plurals
The roots of house are:
hus or huis (old german)
and the plural looked like
huses or husas
which is a pretty standard old way to do it.
The roots of mouse are:
mus or muus
plural:
myys or muys
Not very clear is it? It seems that even in the 12th century 'mouse' had its own nonstandard plural form. My guess is that it was probably borrowed from a different language than other words of the time.
Another animal word which has an unusual plural form is 'goose' " 'geese'
Old Teutonic again:
guus gose
plural:
guis, ges