Tractors tend to spread their load with more, gianter, wider tires.

The trade-off for making the tractor larger is that you can pull wider and multiple or multi-function implements to do the entire thing faster in one pass.

The larger contact patch for having an absurd number of wheels reduces soil compaction and reduces the chance you get stuck; working in fewer passes further reduces soil compaction and prevents you from getting stuck (since in the ideal case, you're doing one pass on solid ground, and never driving over tilled soil).

Tractors get stuck when they drive in mud (and other mud like soils) all the time. However when driving on not-mud it is true. That is the trade off, the heavier you are the more care you need to take about mud.

I suspect tanks get stuck often in part because that is fun and in part because they need to train troops how to get them unstuck and so they intentionally send tanks into mud - which is to say in a real war the generals might (should) avoid getting stuck, but in training it is important to get stuck often. I'm not a military expert though, but that is my opinion on tanks.