The purchasing power of a Bitcoin changes. That's the only thing an end-user cares about.
Do you think that people care about inflation because there are more dollars in existence? No, they care because they can't make the same level of purchases with the dollars they're holding.
Bitcoin's price relative to the dollar indicates what you can buy with it; when that price changes it's no comfort to people that technically the same number of coins exist. They care about what the coin is worth, and Bitcoin's worth can be manipulated regardless of what its supply is.
Do you think that people care about inflation because there are more dollars in existence? No, they care because they can't make the same level of purchases with the dollars they're holding.
Bitcoin's price relative to the dollar indicates what you can buy with it; when that price changes it's no comfort to people that technically the same number of coins exist. They care about what the coin is worth, and Bitcoin's worth can be manipulated regardless of what its supply is.