Why two forms for annotating style of text?

Question

When I want text to be large I say:

{\Large lorem}

When I want text to be bold I say:

\textbf{lorem}

Why the inconsistency? What's the implementation detail or philosophy behind these two different forms?

Answer 1

You're missing the fact that there's also

{\bfseries lorem}

Font-switching/formatting commands come in two varieties: A command that takes an argument and applies its formatting only to that argument (\textbf{lorem}), and a switch that will apply until counteracted by another switch or the end of the group the switch was enabled within ({\bfseries lorem}). Note that the "argument form" is meant for short text fragments, as it doesn't allow a paragraph end within its argument.

One can imagine font size commands like \textlarge which would act like \textbf. IMO, the reason that the former commands don't exist is that (contrary to formatting commands) there's no practical need to switch to another font size for short text fragments. Non-standard font sizes are rather used, e.g., for footnotes and perhaps quotes, and the font size switch is part of the respective command/environment definition.