Hope that you have read this:
Another point of interest is to compare the number of debutants and the number of Tests played by a team. These are summarized below:
You can see that:
New teams (Afg, Ire) are just starting out and need to try out more players.
Australia, Bangladesh and India did not need that many new players.
Among the major teams, South Africa was the most unsettled, introducing 8 new players in 8 Tests giving a ratio of 1.000. Next are Pakistan and West Indies each with 4 new players in 6 Tests (0.667).
Next are England (0.500), Sri Lanka (0.375), New Zealand (0.250).