"why not buy bitcoins with fiat you sell goods or services for instead of giving large discounts to those who pay in bitcoins?"
Yes that way you can buy more bitcoins, but in the long run what will happened is that people will get the idea that they need to buy bitcoins in order to buy cheaper so the demand/price for bitcoins will go up and at the same time the prices of the merchandise in BTC will go down or stay the same so it will always be cheaper to buy with BTC and the BTC you are getting will keep going up in fiat terms.
If it is just you who are buying bitcoins with the profit from selling goods or services it will not really affect the BTC/USD price but if it more and more people who are buying bitcoins it is a trend.
The state/bankers are in power not because they sell goods or services for high price but because you use their inflationary notes
if you start using deflationary commodity as a mean of exchange you get the power.