Serious answer?

Not in any particular order:

1. Military aid to Israel is a defacto rebate for all the stuff they buy and a subsidy for the US defense industry. A lot of US politicians are on the military industrial complex payroll or end up working for it. A lot of Americans work in related industries.
2. Just like with Europe, pushing them to buy American weaponry, ensures their native defense industry can’t become a significant competitor. (Obviously this is an issue in Europe right now, given we’ve been caught with a pants down because we’re too reliant on the US defense industry) For example, wouldn’t want the Israeli defense industry to develop their own highly capable missiles, because they might end up selling them to parties the US doesn’t want to have advanced tech, eg. some Israeli companies were found to have illegally sold China cruise missiles a few years back. That kind of thing would explode if the Israelis were independent for defense.
3. Strategically interesting to have an ally in the middle-east, especially one with an excellent (foreign) intelligence service. Giving Israel aid also ensures neighbours don’t do anything stupid. A powerful military is the best deterent. A powerful conventional military, also avoids Israel going nuclear.
4. Not the worst regime the US supports/has supported. Enemy of my enemy Real politik.
5. AIPAC
6. Evangelicals
7. Outdated views of what Israel is actually like and a language barrier that has allowed Americans (and American reporters) to ignore the stuff not said in English.