When Mahjong first began in China, there were Chinese numbers and words on the tile faces, and there was no need to "translate" these numbers or characters because the Chinese could understand them.
Here is one such set, from the Japanese Mahjong Museum, a beautiful bone and ebony set with inlaid mother-of-pearl backs:
The above set is thought to have belonged to the last Chinese Emperor, so there was no need to translate the East Wind.
And here is a set meant for ordinary people. The Craks are the most difficult to "read"
But when Joseph Babcock and others thought the game could be a success in other parts of the world, they realized there was a need to include Arabic numbers and Western letters on the tiles. At first these indices were added to existing sets.
You can see that the Arabic numbers were put wherever they would fit, and that the tile design did not take those numbers into account.
Later tile faces were designed around the presence of these numbers and letters.
In the tiles above (from a Shanghai Luck set) the letters for the winds were an integral part of the design. On the Craks, the Chinese numbers are a bit off to the right, allowing the Arabic numbers room on the left.
Other sets that were not intended for export were taken out of China. People with those sets either learned how to read the Chinese words and numbers, or they would add them either with a pen or a carving tool.
On the above set the numbers and letters were added later. For whatever reason, the owner was not consistent with the placement of the Western letters for the Wind directions, perhaps because he did not know which orientation was correct for the Chinese word. It was not felt there was a need to put numbers on the Bams or the Dots because they are easy to count visually, as are the 1, 2 and 3 Craks. But once the number 4 appeared, it became difficult, and Arabic numbers were added by pen. The style of game played by that owner did not require numbers on the Flower tiles.