I am your customer, perhaps a happy and loyal one. Therefore, I pay attention to your emails – I may have placed an order on your service, or may be expecting to hear from you.
So I open your emails, especially if they come from the same email domain as your service's notifications do. If many of those emails are unsolicited and irrelevant ads and promotions, you are abusing my loyalty.
Stop taking advantage of the attention of your valuable customers.
As an aside, there is a business opportunity to figure out how to separate service notifications from promotions. Gmail does not seem to do a good job at this.