ARRAYFORMULA does not extend to other rows automatically with this formula using OR. Why doesn't Array formula work in Google Sheets?

This formula works if I drag it down, but the ARRAYFORMULA function is not working as expected.

Formula: =ARRAYFORMULA(IF(OR(ISBLANK(B2),ISBLANK(C2),ISBLANK(E2),ISBLANK(G2),ISBLANK(H2)),0,1))

Why doesn't ARRAYFORMULA work?