Commercial broadcast stations have to pay "performance fees" to Sound Exchange. It is federally mandated in the USA. The fees are based on how many people listen to each song, and must be reported that way. Besides being a huge pain in the anterior regions to figure out, it can be quite expensive to do. The Sound Exchange rate for this year is 0.23 cents per song, per listener. It doesn't sound like much but it really adds up. Let's say you play 13 songs per hour 24/7, or 312 songs per day. If you have an average of 200 listeners over that same 24 hours, that is 62,400 times $0.0023 which equals $143.52 per day. That still doesn't sound too bad, but that is $52,384.80 per year. Keep in mind that the same broadcaster also pays additional feed to ASCAP, SESAC and BMI for their streaming activity. They must also pay for the actual bandwidth used and whatever it costs to file accounting reports to Sound Exchange so they can pay their royalties. Sound Exchange does not send a simple bill, they expect the broadcaster to do the accounting and paper work. That costs money.
Now to pay for this, hopefully it could be ad supported. The problem is there just aren't many advertisers who would pay enough to reach only 200 listeners to make it worthwhile. Keep in mind that most Standards stations are small and rely on local advertisers to stay in the air. If you are not in the advertisers immediate market area, the fact you're hearing their ad is of little value to them. It is unlikely you will ever patronize their business.
Most over-the-air radio stations that stream do it as a service to their local listeners, and do it at a financial loss. For example, it can help keep them stay tuned in while they are at work. That can be a plus, but if the listening audience ever gets big enough, especially if most of it is out of market, it becomes financially unsustainable. That's especially true for small over the air broadcasters which are very often hand-to-mouth operations. Bigger stations can frequently absorb the cost. (But the big corporations seem to have a nasty habit of going bankrupt, to correct for their excess spending habits.) The fee structure needs to change, but it is up to Congress to do that. Until there is a fee structure for streaming that is fair for all parties, I suspect you will see more and more over the air broadcasters turning their streams off.