Abstract variables stay untethered because only variation, not empirical meaning, is required.

Evidence

The role of adjectives is that they demand empirical anchors and thus the input of substantive knowledge. By contrast, the conventional variable (abstract noun) is completely untethered. All that matters is that it offers variation. — Gary Goertz, Social Science Concepts and Measurement, 647

Categorization

• SEED: Essay angle: why so much quantitative social science measures variables nobody would recognize as real, and how the adjective rule exposes the hollowness of ‘it varies, therefore it’s a variable.’
• APHORISMS: A compact working maxim for researchers: if your concept can’t be turned into a predicate someone could satisfy, you probably don’t know what you’re measuring.