[jkaptur]

My pet hypothesis is that train systems are intellectually complex, but bound in a framework of knowable rules. It seems like some people just can't resist diving deep into systems like that (credit card rewards, board games, or, of course, computer programming).

[photojosh]

OMG I think you've just explained my wife's obsession with frequent-flyer points to me. (And she flies a lot, which is a desirable prerequisite.)

[proactivesvcs]

I think you just summed up the reason why I enjoy games such as Factorio and OpenTTD so much :-)

[flukus]

There's something that seems to make train sets much more universal. Compare it to slot cars which are nearly identical technologically but don't have the same geek cred. The only complexity difference is that you get some track switches if you're lucky, but I remember some slot/rc car systems having things like that too. The other big difference is the speed, maybe being slower let's the analytical or imaginative parts of the brain engage?

[tspike]

Described my Lego addiction to a T.