I agree. You really need an SD card for things to work very well. I have an old Garmin GPSMAP 60Cx with a tiny 64mB memory. But with the SD, I have the whole USA, the whole 24k Topo, plus the MCCCT (Michigan dirt bike) trails.
If you don’t update, you’ll miss only the exits that got rebuilt that you try to use, and any new subdivisions that you visit. I have a relative that lives near Columbus, Ohio and they rebuilt a piece of freeway near her house. I got off into the wrong neighborhood and lost a couple of minutes, but the GPS automatically re-calculated and got me there anyway. I visited a friend in Florida that had a house in a development on reclaimed swamp land where the out-of-date Garmin GPS maps failed totally. The GPS in my cell phone saved the day.
In my car, in the shade, my Android cell phone gets updated by Google’s computers all the time, with construction zones and traffic jams. But, as far as I know, the current screens are not readable in sunlight. What I’d really like is an Android phone that can be read in sunlight, and use any regular GPS for backup when there is no cell signal.