Advertisers don't want you to do this since you're spending their money for no possible gain. They only advertise with the expectation they'll earn more than it costs in new sales. Too many clicks for the purpose of donating to website owners and that won't happen, so they'd have to stop advertising.
Networks don't want you to do this because if advertisers can't make a positive return on investment, it doesn't make sense for them to advertise with that company, and they'll go elsewhere or go out of business. Either way, it's a threat to the network's existence.
Morally, it's very much not OK, for two reasons:
1) Small businesses have to market themselves to make people aware of what they're selling in order to survive. Simply opting out of advertising because some people are abusing it to give their money to website owners is not an option. Neither is advertising somewhere else for millions of businesses; Google controls too much of the ad space and traffic. There are no substitutes in many situations.
2) If you work a normal job, telling advertisers to accept this situation is the same as telling you that a condition of receiving your paycheck is that random people on the street have permission to reach into your pocket and take some money out whenever they want. That's what clicking on ads just to give money to website owners is. You may or may not have enough left over to pay your bills. Sound good?