Edit: Apparently glass cookware and drinking glasses are often not recyclable. This seems like a more important aspect to improve than durability even if, again, still overall a small improvement compared to overall glass industry.
Broken glass has to be cleaned up, causes injuries, even causes lost product in some situations.
I was in a cocktail bar once with three friends who ordered us the same chilled cocktail, served there day in, day out, and as the cocktails were poured into the glasses, three of the four glasses broke. Plink, plink, plink.
Glasses too hot, cocktail too cold, some other handling problem. Who knows. But tougher glass might not have done that.
Make all glasses recyclable. Probably more important but less marketable for a new startup idea...
Ironically, most of his patrons were medical students.