Political donations are not a necessity for the country to work properly.
Pets may be a luxury, but once you have them feeding them is arguably a necessity. What's missing is whether they are buying more luxurious food than necessary.
Anyway, in the end it's a completely arbitrary comparison.
Point taken about having to feed them once you have them.
And I agree that political donations are not a necessity, but only if donations are banned, which is not the case. If your opponents are getting donations, then you are at a net loss if you don't. In that sense, being idealistic does not get you supporters, and donations really are necessary.