The Nobel is awarded for actual experimental discoveries and validation of theories, not just unproven theoretical speculation.
Weinberg, Glashow, Salaam (1979) were theoreticians, but their theories for electroweak unification had been validated in many experiments during the 1970's, especially weak neutral currents at CERN in 1973.
Higgs & Englert (2013) had to wait for 50 years for their theory to be validated. The ATLAS & CMS experimentalists who discovered the Higgs particle were passed over, but they outnumbered them ~1,000:1, and only up to 3 people are allowed to get the prize in one year.
https://physicsworld.com/a/overlooked-for-a-nobel-the-cern-p...
https://www.theguardian.com/science/life-and-physics/2013/oc...
However, Rubbia & van der Meer (1984) got the prize for discovering the W and Z (ultimate proof of electroweak unification) on behalf of the large CERN SPS collaboration.