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

Tear everything up and upgrade asap NOT really.

Sure.  Everything matters, so why wouldn’t upgrading internal cables.  But, you’re messing with the voicing the original designer intended and that works with the drivers he’s using and the crossover he deigned using the existing wires.  Cables are so situation specific, I’d think your about as likely to degrade the sound as improve it unless you have the blessing of the designer. 

Doesn't the entire DIY and professional mods folks deal with this part of it all?

I have been upgrading what most companies ignore,out of site,out of mind 

most companies use at best average Xover parts the Xover is the. ♥️ or the 🧠 

of the speaker it most cases even with great drivers a weak link 

I look fir gems or speakers say 5+ years old and rebuild them I just spend $1500

on all the Xover parts for a beautiful pair of Dynaudio Contour 3.4LE  parts quality average like Solen and ceramic resistors ,I use top Either Mundorfs great new Ultra copper foil resistor ,or the close second Path audio from Poland  $30 each vs the $2  in your speaker,  and rewire I bought high quality Cardas wiring Occ copper 

and WBT  connectors , this$1500 spent will turn a $7 k speaker into a $15k+ With ease, a  profound improvement ,it’s Xover is  actually a bottle neck for most stock speakers .after 20 years  I have literally mega 1000s of hours in comparing and listening. Buy a custom built speaker,  Tony Gee of Humble homemade hifi capacitor test  makes great speakers for all budgets check out the capacitor test it covers 95% it pretty accurate ,