I think one big thing is that it's easier to to hire proper lighting designers who will work with the architect during either the initial building construction or a major renovation as there's more leeway in the budget to hire a design, specify better quality and designed luminaires, properly plan out the lighting layout, etc.

Retrofits on the other hand, are probably ordered by the bean counters, and probably are budgeted in a way that favours the cheapest possible products and installers with the mindset that they are doing this to save money so often times you end up with the LED panels, fly swatters, and UFO highbays.

Over the years, I've collected quite a few pictures of interesting lighting retrofits over the years:

400w MV recessed cans with F96T12HO cover lighting, replaced with LED tape on the sides
Stem mounted 2x40w T12 louver? to 1x32wT8 specular reflector strip
Single F40T12 louver strips (in a large rectangle) to two 2x4 (2x F32T8) surface troffers
2xF40T12 louvered fixture to single F32T8 wraparound (Note: installation  no longer exists, after a renovation a new drop ceiling was installed and 2x4 LED troffers were installed.
Recessed F40 fixtures integrated to slat ceiling with 100w MV recessed accent lights to surface F32T8 wraparounds
2x2 400w parabolic MH recessed to LED corncob and suspended LED strips
4x F96T12 turret strips to hanging LED bulb string
F40T12 tandem turret industrial to F32T8 industrial
400w MV? shoebox to 175w MV yardlight
Incandescent highbay and RLM to F96T12 and F32T8 fluorescent striplights
High wattage incandescent pendant to 4x 400w HPS highbays
Recessed 4x F96T12 strips to surface mounted 2xF32T8 tandem strips