Why fourth rates appeared on distant stations

Were fourth-rate ships rare in the Royal Navy?

They were relatively rare in European fleet service but useful on distant stations because they were cheaper to crew, while the scarce first, second, and third rates were concentrated against major enemy fleets.

A third rate might serve as the flagship of an Indian Ocean or China Station squadron. Fourth rates and frigates supplied much of the remaining strength because they demanded fewer men than the largest battlefleet ships. First, second, and most third rates were concentrated where the Royal Navy expected to face major European fleets. That distribution made an East Indiaman resembling a fourth rate entirely plausible in the theater.