There are a number of ways of looking at old photographs. One is as artefacts, historical pieces, rather like pottery shards which should be preserved in their original form with the minimum intervention. Another is, when the photograph is of someone important to you, as a memento of that person, regardless of whether you were able to meet them, or if they died before you were born or were cognisant of their existence.
The joy of restoring and colouring old photographic images is that the originals remain untouched, but we restorers/colourists are able to bring to life those people who are now gone from us. Repairing the damages of age and poor storage is a very skilled job, and we are fortunate indeed on RC to have a number of very skilled restorers, so that photographic images can be cured of their blemishes, and some idea of the true, original image can be seen. With the colouring, to my mind (and I have to, in fairness, declare an interest here) my feelings are that by colouring these old images, we in some small way try to bring back those long-dead people to life, so that we can glimpse back into the past and see for ourselves what our great-grandparents or great-great-aunts might have really looked like.
Photo restoration and colouring is just another way of embracing and rejoicing in the things we have been gifted from the past. There are no objections - as far as I know - to damaged paintings being restored, or broken china being repaired. So why should we not spend our time restoring and colouring old photographs, and rejoicing in the heritage we have been bequeathed. And one of the most important things is that the originals remain as originals; these restores and colourings are interpretations of the original, and help us to reach back and embrace the past.