The value of bitcoin increases because people speculate, not because the number of them is fixed. I bet there are hundreds of crypto currencies that have fixed or decreasing stock that keep losing value, or are already worthless.
As per Satoshi himself, the value of bitcoin increases because people speculate, start using it more, speculate more, start using it more, etc.
The reason why it is capable of increasing, is because the number is fixed. Inflation would outstrip its value, if it weren't.
Bitcoin is useful. It has organic support. When it comes to storing value, other coins do not matter (nearly as much). Just ask PayPal, Mastercard, Microstrategies, Tesla, JP Morgan, GrayScale, etc.
