Bitcoin is volatile. That's the main issue. You can't say that about the dollar or euro.
Now imagine you get paid in bitcoin, save every month for a holiday or a high value purchase. When the time comes to make the purchase you find out that your savings are worth less than 10%. How does it feel using bitcoin?
I tried to use bitcoin(as a merchant) but due its volatility it makes no sense to use it(as merchant or buyer).
At this point, it's a feature to have things denominated in $. I'm likely going to buy a Purism laptop with bitcoin, but of course denominated in $. I spent a couple hundred on BTC years ago, which has generated a nice return. This will be my first purchase, and I'll have plenty of BTC left over. Holding a deflationary currency while the world operates on an inflationary one is fine by me.
I guess they have the shopping list ready by the time they get paid otherwise chances are they end-up with less(or more, it becomes a gable) value by the next day. Not to mention the exchange rate(i.e the employer uses a rate, the merchant a different one...). In the real life people don't like to gamble their wages every single day. They want and need a stable currency and low fees. Bitcoin failed to offer any.
Because to claim that bitcoin succeeded as a payment/salary method is ridiculous. Vast majority of bitcoin volume is just speculation on exchanges. The massive price volatility is a testament to why it cannot be used as a currency -- who would want to make a services/job contract that in a matter of a year could change its value by an order of magnitude. The whole point of these contracts is to hedge against future volatility. Remember, if bitcoin goes up then the employer gets screwed, if bitcoin goes down then the employee gets screwed; there is no direction that is good for everyone, only stability is good.
Furthermore, good currency should encourage investment (into things) which means it needs to be (slightly) deflationary (to introduce a cost to not investing into production). Otherwise you get into a paradoxical/toxic situation where NOT producing useful things becomes financially advantageous.