Fonts have dosens of things added: Unicode to glyph mapping, horizontal writing metrics, vertical writing metrics, kerning, hinting, bitmap fallbacks for small

Fonts have dosens of things added: Unicode to glyph mapping, horizontal writing metrics, vertical writing metrics, kerning, hinting, bitmap fallbacks for small sizes, metadata for aligning baselines and justification, grid-fitting and scan-conversion data, glyph substitutions (e.g. ligatures, old style numbers, contextual, chained), glyph positioning (e.g. diacritics, Arabic diagonal baseline, contextual positioning). Hinting is probably the most complex feature. TrueType implements hinting as special instructions in an impressively complex stack-based drawing language. SVG fonts are already bloated, and adding hinting may have been a step too far, or perhaps it was because at the time some of TrueType's hinting instructions were patented.