A lot of that is thanks to the open source nature of the fonts, and a little sprinkling of Google doing the work to ensure all the license terms are managed through Google Fonts. Nowadays there are thousands of excellent, professional grade typefaces available in a complete distribution, hand-tuned for italics, bold, semi-bold and beautiful to use online and in print. Special characters? What, are ya kiddin’ me? Turned out that each individual font was poorly implemented, with broken letterforms when they were large, incorrect kerning hints and common layout pairs like “fi” completely missing.
I can remember when you purchased typefaces one by one, and that there were companies offering up discounted collections because they acquired them cheaply.