Your dad might be right! This is from NICE (British recommendations for national treatment, a very sane system in my opinion, they try not to waste public money on things that don't work or are too expensive)

The manual therapies reviewed were spinal manipulation (a low-amplitude, high-velocity movement at the > limit of joint range that takes the joint beyond the passive range of movement), spinal mobilisation (joint movement within the normal range of motion) and massage (manual manipulation or mobilisation of soft tissues). Collectively these are all manual therapy. Mobilisation and massage are performed by a wide variety of practitioners. Manipulation can be performed by chiropractors and osteopaths, as well as by doctors and physiotherapists who have undergone specialist postgraduate training in manipulation.

1.4.1 Consider offering a course of manual therapy, including spinal manipulation, comprising up to a maximum of nine sessions over a period of up to 12 weeks.

I have found over the years that a single session every year or so obliterates a problem that, if left unmessed-with becomes painful and eventually restricts my ability to play various sports.

The first time it was done (I was about 25?), a short-sighted friend blanked me in the street because the way I walked had changed and she didn't recognise me. She said the way I walked had been very characteristic, and now it was more normal!

I don't know what NICE are basing their recommendation on, they could conceivably be going after a cheap placebo effect.

P.S. My nice chiropractor says I have: Ilio-psoas hypertonicity secondary to Sacro-Iliac instability.

P.P.S. Careful. Chiropractors are loonies. Their explanatory theory is rubbish. My personal chiropractor is great. I would be very very suspicious of even her colleagues, let alone the rest of her profession. On the other hand, at least they are trying obvious things, to see if they work.