It's harder to move having a house, certainly (which I do), and where you live or move to will affect whether you need a car or not. In some ways, by
not having a car, you're limiting your experience by saying "I'll never consider living in these places". That's OK, but it does have an impact. Likewise, if you wanted to
have a car, you're sometimes restrained by the cost of
parking the car in certain locations.
Gas - certainly a concern, but so is bus/subway fares, which replace gas if you don't have a car but still need to move around.
Taxes - for 2 cars we pay about $150/year.
Insurance - possibly $1000 per year.
So... maybe $100/month for taxes/insurance on 2 cars - for most people this won't break the bank. This also allows us to live in a more rural area with a somewhat lower cost of living (lower taxes for a start).
Maintenance - yeah, some. I don't think we worry about it, much like you don't 'worry' much about your electric bill or internet bill. It's a factor in life - there are repairs that come up, but again, the ability to be mobile when we want, in areas that aren't otherwise served by mass transit - is, for us, a plus right now.
Replacing gas/tax/insurance with monthly subway tickets, which I'd probably need to do if I lived in a major city, seems like it might be about the same (IIRC, a two week pass in Moscow cost be about $50?).