In markets like China, where there is a universal service like WeChat aka messaging, purchases and all the other shit. The cost of switching OS is smaller therefore it happens more often.
In the UK, if you primarily use the phone for messaging and social media and you are using whatsapp, the cost of switching os is small. This is not true for markets where imessage is the dominant messaging platform.
Regarding the other point, the Senate doesn't need to concerns so much if it is currently illegal, just whether it is good for consumers and producers and then they will legislate accordingly.
I still have no idea what you're trying to say regarding "the cost of switching OS is smaller", but regarding the last part about the Senate: that is precisely the point I'm trying to make. If the Senate passes this bill under the pretense of wanting to help the consumers this would have major ramifications for companies (not just big tech), and it sets a dangerous precedent. In fact, it could end up harming the consumer because innovative businesses could (and would) be told that their product is not allowed to function the way that it does, even when they aren't engaged in monopolistic activity.
Think about this: if you create a piece of software that relies on a marketplace you designed in order for you to make a profit, this bill would effectively kill your product. Other developers would tell customers they have to use the developer's own marketplace instead of using yours, therefore preventing you from making money off of the software that you created. That's what this bill does.
That's not pro-consumer. It's pro-developer. And we all know that nearly all developers do NOT pass any savings onto the customer. If shipping prices decrease the product price isn't decreases to reflect that. Digital games cost the same amount as physical games even though it costs the developers FAR less money for digital content. So Epic Games Store winning this lawsuit, or Congress passing this bill, results in developers getting more money but on the backs of someone else's work (specifically Apple in this scenario), and that doesn't end up benefiting the consumer at all.