Some of the older equipment with narrow tires (and high inflation pressures) did do a lot of damage.  What we have happening with today's very heavy machines is that it isn't simply a matter of going to ever-larger tires, although that helps enormously.  As the area under the tire (or track) increases and it covers a lot of soil, it can drive the compaction deeper.  Deep compaction is slower to heal itself by shrink-swell, roots, mycorrhizae, earthworms, etc.  The point is that while you should use the largest radials at the lowest recommended pressure, there may be limits to the axle load that can be carried without substantial damage.  I.e., with the most gargantuan machines, tracks may become crucial to mitigating compaction.  However, tracks do create one additional issue on machines that have a lot of vibration (tractors & combines), as the track system transmits more of this vibration to the soil -- and the vibration is bad for breaking down soil structure. 

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