Python re.findall() is not working as expected

I have the code:

import re
sequence="aabbaa"
rexp=re.compile("(aa|bb)+")
rexp.findall(sequence)

This returns ['aa']

If we have

import re
sequence="aabbaa"
rexp=re.compile("(aa|cc)+")
rexp.findall(sequence)

we get ['aa','aa']

Why is there a difference and why (for the first) do we not get ['aa','bb','aa']?

Thanks!