However if you're behind an IPv4 CGNAT, that does apply a lot of limits to what you can do with your Internet connection. Not only can you not receive *any* inbound connections at all, but you are sharing a public IP address with other people: so if one of them does something bad, Plod may come knocking at your door.
Having Plod come knocking is perhaps a tad extreme. It would have to be pretty serious for them to go through all the ISP's routing tables to distinguish me from all the other concurrent users of that public IP, though I'm sure GCHQ could do that easily if they wanted to. But being behind CGNAT for the first time now, I do find:
1) there seems to be an increased incidence of those wretched reCaptcha things (pick all the squares with US style fire hydrants);
2) I have an issue with email non-delivery to some contacts, which is very hard to pin down as they just disappear completely, but I suspect has at least something to do with the reputation of someone/something else sharing my IPv4 address;
3) I'm not bothered about hosting games or websites locally, but I can't run a BQM.
Or also c) question whether there is any actual demand from their customers.
In Swish's case at least, this can not be the case, I have made my views very clear to them, as I know others have too. I don't see why I should pay extra for a static IPv4 to work around a glaring deficiency in their network. I have told them I will not recommend Swish to any friends or neighbours until they fix it. I would leave myself if I had an acceptable alternative.