That's great. Do it. Remember, there's no "they". There's only "we" or "I". In other words, don't say, "Why don't they do this?" because "they" is really "us".
I'm actually developing an online business and I'm going to include Monero as a payment option. I'm not waiting for "them" to do this. I am doing it. I'm going to offer a discount for using Monero, too. In order for a new currency to be used, the consumer will have to be able to buy something with the new currency that he/she CANNOT get with the old currency. I would offer a 10% discount over credit card because for online visa/master payments, most processors charge 6 to 7 percent for low volume merchants. Then, refunds eat up another 2 to 3 percent. So, it's about a 10 percent difference between credit cards and Bitcoin/Monero. Typically, about 2 percent of consumer purchases, the consumer wants to keep private. Monero could fill that need. Therefore, at about 2 percent of Bitcoin's market cap, each Monero should be worth 20 times what they are worth today.
:-)