Why can't Canon learn from Apple and just make something that "Just Works". If my iPhone can have a GPS receiver built in, and there are pocket cameras with GPS built in, why isn't it built in to all of their DSLRs? If the photographer is worried about battery life, they could switch it off.
It is ridiculous what you have to do in order to get real time GPS values into the metadata on the 5Dm2...
I'm guessing they don't build it in because the vast majority of people could not care less about this feature. Most of the photographers I've spoken with who use similar equipment don't understand why I care about this feature and have no use for it.
For the very, very small subset of the community that does want it, there are solutions available that are improving with each generation. When I had my 5D2 I had to use the data-logger approach and it drove me crazy but now with the 5D3 it's a cleaner solution that works a lot better for me.
Every single product any company makes is about a selection of features that they emphasize and features that they de-emphasize. You cannot put every feature that every potential customer might want in every product; you'll end up with something nobody likes and nobody can afford. It's not unreasonable to conclude that Canon's market data suggested that while there is a portion of the market that desires this feature it's not one large enough to warrant building it and it's associated costs into every device. They chose a balanced approach where the feature is available for those who want it but most who do not are not required to pay for it.
It's also not clear to me whether there would be problems with the GPS signaling if the antenna were put inside of the magnesium body as opposed to the external plastic case. I'm not a radio engineer by any stretch but radio signals don't typically go through metal all that reliably.
I won't debate the cost topic because that is a subjective for most and it's either worthwhile for you or it isn't. Of Course I would like it to be less expensive (like everything else I purchase) but the workflow benefit it's providing are worth the investment for me.