Filters were one of many improvements and advances on tractors just as on cars.
For many years there where no oil filters either, petcocks on oil pans to check
levels. Then we got screens for engine oil and later filters, many a toliet paper oil
filter got added to tractors, trucks and cars. Many early oil filters were bypass filter,
they just took a slip stream of oil to filter and return to the pan, the clean oil wasn't even circulated.
Sediment bowls with screens for fuel filters. As tractors and engines advanced so did filters
and transmissions and hydraulics went from being available to being necessary.
Now hydraulics are a major part of a tractor. Pressure has gone from a few hundred pounds
to a few thousand pounds, the cost and performance of the pumps and the tractors has evolved immensely.