Others are rightly pointing out "laptops are bigger so should have better reception" (assuming it's physically taking advantage of that, which most built-in do)

Others are rightly pointing out "laptops are bigger so should have better reception" (assuming it's physically taking advantage of that, which most built-in do) but the modems in most laptops have been historically bad with the modems in phones top of the line (as well as often refreshed more often). That's of course not a requirement, Apple could choose to put in the greatest modem they can make. That combined with good antenna design in the MacBooks should lead to significantly better reception. The limit of this is how good the modem is. Given how long they've let it slip my guess is they won't release it until it's very competitive, similar to how long they took to dump Intel despite the iPhone processors being competitive with the likes of the Intel m3 well before that. Time will tell on that one. The other half of the story is Apple has already ditched SIMs for eSIMs in the iPhone. It'd be extremely odd if they then went backwards on this to put a SIM tray in the MacBook, a device they are regularly reluctant to include more than a couple of connectors on in the first place.