What's the benefit of 24V over 12V in solar and charging?
The benefit of a higher voltage is relative. It depends on distance, and power level.

If your panels are right next to your tent, the batteries inside, and you're just running a few LEDs, then 12v is just fine.

If you want to run several hundred watts, and you have distances of 10m, then the difference is very significant. Not only smaller cables, but smaller connectors, and often smaller and cheaper equipment. Why cheaper equipment? It has cables, fuses, PCB traces, connectors inside, and active devices at 100v are not 2x as expensive as 50v devices.

To put some numbers on that. Let's say you want to run 120 watts over 10m, this is 10A at 12v. Let's say you're using 1mm\$^2\$ cable. The resistance of 20m (out and back) is 0.34 ohms, giving you a 3.4v drop at the end, or 28% of your power. Running 5A at 24v, you'd lose 1.7v, which is 7% of your power.

Other things being equal, you can run 4x the distance, or use 4x the power, or have much more scope for future expansion, by running the higher voltage.

48v is a common industrial voltage, used for building-sized DC power. It's the highest voltage you can go to and stay 'touch safe' 'low voltage'.

Of course when loads get to kW and distances to 100m to 1km, then 240v gets useful, and at MW and 10s of km then 100kV + is the norm.