Why doesn’t Gregor recognize his father in his new uniform in "The Metamorphosis"?

I find it highly ironic that, if we examine this excellent
short story carefully, we can see that by far the biggest transformation is not
experienced by Gregor himself, but by his family, who suffer their own metamorphosis
thanks to the change in their family life that Gregor's metamorphosis brings. The father
is just one example. When he rushes in because of the sound that Gregor's sister makes,
Gregor finds it hard to recognise him at first. Before, his father was always exhausted,
incapable of standing up and could only walk slowly is a completely different
person:

But
now the father stood quite steady; in a snug blue uniform with gold buttons, such as
attendants in banks wear; his heavy double chin unfurled over the high stiff collar of
the jacket. From under his busy eyebrows, the black eyes gazed fresh and alert; the once
disheveled hair was now glossy, combed down, and meticulously
parted.

No wonder, then, that
Gregor has a double take before he can identify that this man is the same father who has
changed so much by the need to go out and get work and provide for his
family.