The SD card slot was made more important by Apple's decision to move both USB ports onto one side, meaning that one standard SD adapter covered both ports. 🤦‍♂️ If there were 4 USB-C ports on laptops, 2 on each side, this would be less of an issue. Plus, with wireless transfers straight from cameras, along with easy USB to USB transfers, the SD card slot isn't as important as it was in 2010 (though of course it's still important for pros that shoot a lot of images or footage in high res/RAW).Yes. The SD card slot in particular is a huge selling point for many Pro buyers. It was a big deal when Apple added it back (along with HDMI and MagSafe) on the 14-inch MacBook Pro.
Apple would certainly not bother putting these things on their Pro laptops if only 10 users wanted them.
That port is in a bit of a unique situation and impacts professionals but very few hobbyists. If it makes you money it's easier to justify an extra ÂŁ500 or so to dodge a dongle.