to give a clear and short answer to the question "requirement to wear safety glasses considered an industry standard in the warehousing industry for Forklift drivers?"
no, it is not "an industry standard in the warehousing industry for forklift drivers".
However if there is any chance of material being blown into the operators eyes, or other people in the immediate vicinity doing work that requires eye protection, then the same level of protection should be required for powered industrial truck operators.

LBA RR:

The following U.S. OSHA General Industry Regulations apply:

Using the Google search engine, search:

OSHA 1910.132 - General Requirements

( also search ):

OSHA 1910.133 - Eye and Face Protection

If eye protection is being used for impact protection, it must include side protection:

"OSHA 1910.133(a)(2)

The employer shall ensure that each affected employee uses eye protection that provides side protection when there is a hazard from flying objects. Detachable side protectors (e.g. clip-on or slide-on side shields) meeting the pertinent requirements of this section are acceptable."

Safety glasses can be required for many reasons:
1. A company safety standard policy.
2. Personnel are working around machinery or hand tools, air born particles, etc.
3. I'm certain the OSHA manual can give you more information on when where what type are required.
4. There has been more than one forklift operator that has had a metal flake in his eye from the mast channels or rollers.