and they asked, why?

When I told the people at work that I was engaged, this is what they said:

"Really? But why?"

So, I get it. I'm working with kids (figuratively, not literally (yet)). With people who love going out every weekend and getting sh-faced, and when they can't remember what they did Saturday night, it must have been a good night. We get paid every second thursday, and quite often they're 'broke' by Monday, and (god forbid) barely able to buy cigarettes on the wednesday before pay day. They are drifters, who don't know what they want to do. Maybe they'll become a Team Leader (of a team in the call center), because, well, they've worked on the phones for long enough that that's probably the next logical step. They complain about the pay, the customers, and job, but they stay on because it's easy, and if you do ok, you'll get $23 an hour and hey, that buys a lot of booze. Sometimes they leave. Six months later they'll be back, as though nothing happened.
I work here too, right? But for me, it's always been a time-filler. It will have filled 3 years in Feb. That's a little ridiculous, but it's been what it needed to be: A way to save money for my trip to Europe, a way to get out of school for a year or 2 and just make money, work full time, meet people. A way to work very little while I do my Masters, by being flexible enough to let me work when I want. A group of us 'oldbies' did a 'point of view' survey yesterday. One of the aspects we brainstormed was on 'Belonging'- what makes you stay within the company and within the project? My brutally honest answer: the fact that I can work 5 or 10 hours a week while I'm at school. That I can take 2 weeks unpaid leave for teaching rounds. That I can work full time over winter and summer holidays. That I can still take 6 weeks leave and know I have a job to come back to.

But it only just stuck me, 2 months after my engagement to Nic, that some people here had asked why. Not everybody, that'd be a generalisation. But enough.
Why do we do anything? Why date somebody? Why work here? Why move house, or get married or have children either? Some of those have logical answers of course, but why get engaged? I still don't know what the answer to that is meant to be.
Because I want to?
Because I like him? (I love him, this is just a bit of an inside joke)
Because I'm happy?
Because we want to get married, eventually?

I don't know- are you MEANT to have an answer to that question? It's not really a question you get asked! I didn't think so, anyway.
Who knows, maybe they were trying to suss out if I was pregnant or something.