They can make sure that their presentation appears on the projector screen the way they designed it.
The designers who suggest using newer ones are giving presentations in an environment where they have more control over things. There are certain types of presentations where using these fonts is more feasible. You cannot simply use a new font wherever you want. This advice may seem great at first, but using newer fonts has some disadvantages as well. Most presentation designers suggest using cool and interesting fonts to make your presentation stand out.
Making a decision about what fonts to use can confuse many presenters.
