This is how most couples get together at workplaces or at uni, spending a lot of time with each other. It is because trust gets built, which is the base for any relationship. But don't forget that these relationships usually are not the most healthy ones because for most people it is the only way to get into a relationship, and thus they take what they can. Picking up girls on the street gets you less trouble and makes much more fun.
Surely "picking girls up on the street" doesn't constitute a relationship at all, or at least it's just a casual one. Maybe that's what some people want but I certainly wouldn't say that relationships founded on trust aren't as "healthy" as casual relationships. Everyone is different - but there's no need to pretend that any group is better than another.
For me the most interesting question is why these relationships break up so often. I believe it is because most men only get to know women at their workplaces (or being drunk at parties), and therefore only have a very limited choice of women. Consequently, their chance to end up with the wrong partner is very high.
How else could men meet women that you think would be better? For someone my age (25) it doesn't really seem like there's that many different ways of meeting women - at work, through friends or whilst out drunk. That's how most people I know met their partners.
That's sad. But have you compared that to the number of drunk-pub-romances that have also failed?
I think the BIG difference is decided by whether you're out for just a nice one-night-stand, or for something longlasting & serious.
BTW, lest-we-forget, some 30-50% of ALL relationships fail in the long run (at least in the Western world), wherever the couple happened to meet in the beginning.
You said it...
...and my story...
I've been seeing my girlfriend for 8 months, she used to be my boss at my old job. I guess it's not technically a workplace romance because we started seeing each other after i'd left but yeah, I think knowing her as I did at work definitely gave me a good idea of what she was like.
I used to feign incompetence so I could have an excuse to go and talk to her, it was fun and at the same time it was pretty harmless - it didn't majorly affect my work and it kept her in good spirits when she was feeling stressed

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I can't really speak about working with your partner (which, if I had to guess, I would say could be pretty awkward - because every couple needs plenty of time apart), but i'd definitely say that work was a great place for me to get to know my girlfriend before I started going out with her. A lot of women have a sort of tendency to see men trying to talk to them as predatory, so I think work is a good place to meet women in that maybe they don't put up barriers like they might do if you just met them socially or something - they can get to know you without automatically thinking "he just wants me for the poon". Idk though, can't say all women are the same like that.