Why doesn't BTC depreciate in value as its supply increases? The popular intuition is that that greater supply = less demand. I've looked around and haven't found a counter-argument. Why is the BTC gaining value as its quantity increases?
The popular intuition is typically correct in well-saturated markets, but Bitcoin is not yet a well-saturated market. Though the supply of Bitcoin is currently increasing the demand is increasing dramatically faster. This is because we are during the initial adoption curve of a new technology and new demand is created as individuals discover the new tech.

In short, there is absolutely some downward pressure on Bitcoin's price exerted by the inflating supply, but it has been completely overwhelmed by upward pressure from new adoption.