You can, you just need to download the maps for offline use. Google maps makes it easy:

https://support.google.com/maps/answer/6291838

It's very useful for navigating crowded touristy areas, remote nature preserves, sports/music events that jam the towers, etc.

Some more specialized apps also support doing the same thing with other types of maps, like USGS quad sheets.

I wish you could download a lightweight map of the entire country. The way the selector rectangle works in my city makes it awkward to capture it well since its kinda longer east west rather than north south. If a garmin from 2002 could hold maps of the entire country, surely my iphone with 512gb of storage should be able to do it too.

Use OSMAnd instead, it can download entire country map with a click without dragging rectangles around

I'm still surprised when people are still surprised that this exists.