It makes sense. Throwing a 5kg ball or swimming real fast on your back isn't exactly of value to anyone.
If athletes want more money and are participants in sports that have low interest, they have to first ask where the hell they think that money will come from. I have a friend that competes in long jump on an international level and is also an athletics ambassador. There's no viewership, merchandise, public hype, etc. so there's no income. Dude just holds a good engineering job. Similarly one in triathlon, which he does have some decent prize money and sponsorship as there is much more interest and viewership, but he still works a full-time job and he has to be absolute top of the field to get any reward.
You can't make the public watch things they don't want to. And no one wants to pay for something they're not interested in or want.