even if you can pay in stores with bitcoin i don't think people will start spending their coins. they are probably too worried that when they spend their coins, that the price goes up afterwards, and thus they will miss out on profits. that's how people look at spending their coins. the intention to use it as a currency gets overpowered by the investment aspect.
Maybe some but not all use bitcoin as an investment. Some of my friends readily spend their bitcoin once they receive it. But they also leave some for altcoin trading. They treat bitcoin as supplement for their income. I on the other prefer to save and hold my bitcoin for the future. But there are time I also need to spend my bitcoin for emergency purposes.