Why must field names of messages and services be lowercase?

[Maverobot]

In the design draft, it says

Field names must be lowercase alphanumeric characters with underscores for separating words. They must start with an alphabetic character, they must not end with an underscore and never have two consecutive underscores.

Capital letters in field names can sometimes more suitable and human-readable especially when it comes to mathematical expressions, e.g. in FrankaState. Are there special reasons why capital letters must be eliminated from the field names?