In games where you have fixed betting amounts denominated in BTC, you'll also pay less for those bets.
This is actually a great opportunity to buy Bitcoin for example and get more out of your bets.
Just an example:
Now, when I buy €100 worth of Bitcoin, I can place like 10 bets more on the Crypto-Games roulette.
I get more BTC for that €100, while the minimum bet there stays at 0.00001 BTC
I agree with you. For those buying BTC today to play various games online this situation is a favorable one. For example winning $100 in a poker tournament brings more BTC to your balance than that would bring several days ago, and if you won't lose it or exchange it to fiat right away, most likely your prize will grow in USD value with time.
But OP is wright regarding spending the BTC you already have, in a sense that you should spend more BTC now when placing a $20 bet, than you would several days ago.
Anyway, one should be careful these days about how much BTC he/she is spending when placing a dollar-pegged bet.