Simon -
most can afford a moderate habit.
What does this really mean?
You need money so you can develop a habit?
You only need review the Karen Matthew's TV footage taken on that estate over the 11 days (?) she was "away" to know that those who can least afford it look like they cane the ar£e out of all manner of drugs with little or no disposable income.
The truth of the matter is that, as you've witnessed above, there's a certain disquiet about just what alcohol fails to deliver upon, especially where mtn biking / fitness is concerned. I don't doubt for a moment that it's partly age related, so don't be too judgemental on those who have caned it and one day find it's actually just Fools Gold.
Further more, if you re-read the title of the post, you'll see it was pretty much asking for similar experiences to the OP's. Don't be surprised when people answer truthfully and with a level of candour that clearly sets some on edge and makes them uncomfortable, perhaps mistakenly viewing such experiences as full-on evangelical preaching or even Born-again reverence because it simply is not the case.