Staining and/or dying to match an existing color is far more difficult than it appears, especially over a period of time.
Even if you do manage to get it worked out well enough to pass scrutiny today, it is not likely to stay that way.
The natural aging of the original finish is still present, and all of the "new work" has either removed it or replaced it. (depending on the nature of the repair)
The newly matched parts are not likely to age the same way.