I think you're spot on as usual
Revolution .
I was 16 and a season ticket holder on the Kop that season. I think there are a number of reasons for the low crowds compared to now...
1. The team was poor. After a promising couple of seasons after Brealey came in, he seemed to lose interest after his 'Bramall Centre' scheme was rejected by the Council planners. There was little investment in the team to the point where supporters were directly involved in buying players (Richard Cadette).
2. Unemployment was high due to the decimation of industry in the city, particularly coal and steel.
3. Grounds were no more than run down cages, decrepit old stands and crumbling terracing.
4. The height of football hooliganism. I remember having to plead with my Mum to start letting me go on my own as she was certain I would get beat up or worse. In truth, I never really saw any problems. The worst I saw was Leeds in 1985/86.
5. Little or no marketing. The junior blades had just started and kids sometimes got the odd complimentary tickets but it was nothing like the commercial enterprise it is today.
6. The failure of the national game. English clubs were still banned from European competition after Heysel and England made a very poor showing at the 88 Euros.
The general turnaround occurred, tragically, after Hillsborough when the authorities finally realised that if you treat supporters like animals, they will act like them. England got to the semis in the 1990 World Cup and English clubs were allowed back into Europe.
In the Blades case, this coincided with some success at last with Bassett getting us back into Division 1 and we also had some runs and big games in the FA Cup, something the club had not had for the previous 30 years.