Fair point but when you consider the way in which rail usage has increased over just the past 20 years compared to how much not only bus journeys but also bus mileage has decreased it prevents a shocking picture. Couple this with the fact that urbanisation is increasing (and it is in urban areas where Public transport is more feasible) and that the elderly & disabled are being bribed with free bus travel and it presents quite a depressing picture! Even now London is decreasing in terms of bus use and mileage the decline would be even more sharp. And it is not just in rural areas; patronage is declining sharper in metropolitan areas compared to non-metropolitan areas.
It is a complex picture but I guess I wanted to illustrate that yes, whilst it's correct that patronage has declined since deregulation, it wasn't the land of milk and honey beforehand as some might have us believe. This is despite some rather large subsidies in outright council and fare support subsidy, new bus grants, writing off of debts etc. Deregulation and privatisation reduced that (it was the primary aim) - note that when ENCTS arrived and was properly (ish) funded, that arrested the decline of passenger figures and that when austerity hit, the fall began again.
Take the funding to the rail industry. In real terms, it was c.£1.6bn at the end of the 1980s. That grew to £5bn in 30 years in real terms. That is the difference. If we decided to put in £1bn a year on improving bus priority and infrastructure, I'd suggest that would massively improve things. We've just seen Bristol roll out Metrobus - £250m worth of improvements but when you look in detail...much of the spending is on new roads that, shock horror, also open to cars. Also, remember that there hasn't been a fuel duty increase since 2011 so to protect "hard pressed families" (aka voters) but at the same time, bus drivers' wages have increased (with increased pensions contributions, NI) and BSOG being reduced.
With that backdrop, burgeoning congestion as private car travel becomes ever cheaper in real terms, Clean Air Zones that apply to commercial vehicles but not to "hard pressed families" so increasing costs, an underprovisioned ENCTS scheme and the basic structural changes to how we live, work and shop, I'd be flapping amazed if patronage wasn't going down!!