The premise of excel is very much "don't bug me, just do it". The highly praised UI simplifies away corner cases and errors intentionally. Summing over an empty cell? Most probably zero, why throw an error and confuse the user? The simplified UI makes correctness hard to impossible, so excel is just unsuitable for tasks where correctness is desired.

Interpreting an empty cell as 0 is making an (often correct) assumption about what the user wanted.

Throwing away data without warning is almost certainly never what the user wanted.