Are you referring to Sonos Radio (free) or Sonos Radio HD (paid)? What type of 70s/60s music-rock, pop, country? I think it’s there, it’s just mixed or referred to in a different way. For example Rock Pantheon has early rock n roll. Classic Country ia country and Rare Grooves has R&B, Soul and Funk. No old school Pop as fas a I can see. I do agree it’s not specifically focused and named though. 

On HD, was really looking for chart hits from the classic years of 60s & 70s. Plenty 80s, 90s etc. but for me, the best of times is missing.

Try Radio 10 and Nostalgie extra 60-70 on MyTuner, and All 60s All The Time on TuneIn.