Mostly to save money, in a lesser way its also a side effect of my desire to drive a lightweight nimble vehicle (I love small, well-handling cars, I'd also consider a motorcycle, but I need a car for the cargo capacity), which are often better on fuel than heavy vehicles, especially in busy traffic like here.
I would rant about the taxation of vehicles and fuel over here, but I don't think this is the topic for that. I'm kinda glad for the recent price drop on fuel, its back to the level of 13 years ago. (When the trucking industry protested, diesel going past €1/L ($5.60/gallon with the exchange rate back then).
I actually sold my (sporty, driven with a lead foot) solid 30 MPG car when pump gas here spiked to €2/L 4 years ago. (almost $11 a gallon back then.)
The big downside for me is that its now even harder to justify switching to electric, battery write-off is a real killer on the cost-per-mile equation. Still working on getting an EV. Its also a lot of hoops to jump through to get DIY EV stuff road legal here though, another pet peeve of mine. :/ I might open a topic to rant some more.