Why don't upgrade the wires and components inside our units?

I first explored replacing internal wiring in Ed Long Sonex MkII Time Alignment speakers waaaaaay back in the late 1970s. At that time they were already older speakers, meaning the internal wiring was not on the hifi radar. I replaced it with  Wire World's first gen internal wiring, and painted the insides with many coats of boro-silicate. Due to the tall cabinet, I horizontally inserted a long threaded rod to alter any resonance, and finished the job hanging some wool over the rod. Well worth it

These days, unless you own tube gear there isn’t a lot to be changed, but I found Oppo 105 wire upgrades on EBaye. First, I replaced the OEM IEC with a Furutec long silver tail to connect to the OEM power supply board, fuse jumper, and 110/220 switch. The improvement was not subtle, so I replaced the OEM PS with an aftermarket LPM to excellent results, though eventually I did get a active preamp

My Emerald Physics 3.4 speakers have outboard XOs and came with cheap jumper wire. I ordered WireWorlds newest internal wire but it took a couple weeks to get it. As soon as I made the swap, my first thought was this speaker could have easily sold for an extra $1-2,000

I think DHLabs sells bulk wire

hth

My b&w speakers  crossovers and all wiring were removed and discarded,  I bought a Troels Gravenson upgrade kit from Jantzen and built new ones myself with having zero experience, I couldn't be happier. He has enough information that you can't go wrong. I'm not ready to tackle other gear other than a speaker though. 

I've rewired every single inch of internal wiring on Klipschorns, also spec'd silver litz and diy modded in some Duelund internal wiring on my custom build 300B monoblocks. My 845 SET and pre have no wiring to replace.

Obviously, I've determined internal wiring at least as important as ic, power, all external wiring. DIY capability makes it doable for me. Sending off to tech would be obstacle for me so understand those who haven't done.

I was planning this post for years, just never did it.

How about transformers using only OCC copper (if possible)? I know some companies have made them using pure silver wire (WAVAC?).

Replace all internal speaker wire with OCC.

All wiring in amps and preamps.

Couldn't sound bad!

Sure, you can change out parts and wires to upgrade a component, but, this is a process that involves listening to the results and perhaps back-tracking.  The process involves "tuning" and "voicing" to fit your particular taste and to complement other components in the system.  Any meaningful change in the sound resulting from a component change has the chance of improving or degrading the sound.  It is not simply the case that a more expensive part, or one with a good reputation, will necessarily improve the particular system.

A local dealer that builds his own custom gear under his own brand name once had me listen to one of his amps.  I am quite familiar with his amps, so I was expecting to hear something quite nice.  I was reluctant, but, I ultimately told him that this particular amp sounded like crap.  He smiled and explained that a customer sent it to another company that "upgrades" components and it was fitted with things like Blackgate coupling capacitors and fancy resistors; the customer was so unhappy with the sound that he was having the upgrades undone, which is why it was back at the dealer's shop.

One should approach this sort of upgrading as an experiment, and one should keep an open mind about the results.  I see too many threads on these forums about things like tweaks that seem to always improve the sound--if they work, they change the sound, so how can the change always be an improvement?  I suspect that at least some of the improvement is really expectation bias.