That is not the way things work.
Why does Apple take 30% of sales? Because Apple prices at the profit-maximizing percentage and because Apple figures that the profit-maximizing percentage is 30%.
Lower, and they leave money on the table. Higher, and sales volume goes down.
Ever hear of something called "consumer surplus"? A gallon of gasoline would well be worth $10 to me, but I pay a lot less then that! Why? Because of competition.
In the white darn city here, the prices are within 1 cent of each other and everyone somehow raises them whenever there is any excuse.
Differences between cities are up to 20 percent. Sometimes (not considering externalities) it would be worth driving much farther to buy petrol. Few people do it.
Local monopoly or collusion is as good as global one. For Google Pay, the local is whole main Android store.
Where they do compete with cheaper alternatives (e.g. in South Korea), the premium is lower. But only there.
Facebook essentially guesses a price on their advertisement monopoly on their platform. The price is not set by competition nor by demand, but by belief in value added (which is only partially responsive to supply and demand), just like in most stocks.
I recommend reading on the concept of elasticity and substitute good, as well as idiosyncracies of human economical decisions.
30% is the price, set on the non-monopoly market. I don't get what you are complaining about.
No indie game developer that has been around for a while would say this. A 30% cut is way less than anything else that came before it.
Steam also allows you to sell Steam keys from wherever, and you get to keep 100% of that. This is how Humble Bundle works.
When you release on Steam, you also get free exposure at first, which is basically free ads. You would otherwise pay several thousands of dollars for that.
So in any sense, Steam worked to get that 30%, and there is no serious indie game developer that is arguing with that.
Which is not exactly happily handing over 30% of your earnings to Steam/Apple.
Also, as mentioned in other replies, Apple explicitly blocks any other licencing path unless you're one of the big boys and can afford lawyers etc...
Steam's bigger marketplace and that it removes the uncertainty and risks around payment provider management (chargebacks etc.) easily make up for the bigger cut. Do less work, make more money. It's not unreasonable.
I'm not saying Apple don't provide a service, of course they do, though at times it sucks. My main point is about is about the price, not the principle. I pay Apple a yearly subscription just to develop for their platform. On top of that every sale I make they get 30%.
Would 95% be ok?
Another extreme element of this is that I cannot sell a licence outside of the App Store to my customers. I cannot ask them to buy from my website (which many have asked about and would be happy to do) and provide them with a code they can use to unlock or upgrade. This is explicitly banned. Unless you're a big player like Spotify or Netflix your app will not be allowed to do this. I've tried and been denied and stonewalled.
In this case I am willing to build and manage my own payment/licencing setup to gain 30%. I'm just not allowed to do that.
And I don't, tbh, have an opinion about the rest of your post; I'm talking about Steam, not Apple.
But, having gone down this road myself (and why I cite the Jeff Vogel talk): you would almost certainly spend more than 30% on customer support and payment processing and fraud protection and accounting. Or you would do it incorrectly, which is worse. And, regardless, you'd expose yourself to a way smaller audience. It seems to me to be a good way to shoot yourself in the foot for no gain (and as an app developer myself I certainly wouldn't bother).
I explicitly cannot do this for iOS apps. There is just no way for me to get my app in front of people's eyes without paying the Apple tax.
If I was prevented from distributing my movie somehow by Disney, you might have a point.
Disney's not going to put it in their online store, though.
In the case of an iOS app, you can sell the source and let people build it on their own Xcode installs, if you like.
Then we'd all have a half dozen completely incompatible physical media players and so on.
I'm thinking about Craigslist, Snapchat, Vimeo, Mixer, etc. Don't confuse market leader with monopoly.
Before Steam, you had several casual portals (all competing with each other). Do you know which cut they took? 70%.
Do you know why platforms nowadays take 30%? Because it's well worth the 30%, that's why. And if you think a platform can live off a 3% cut, please show me the successful on that does that.