one reason..
When copper wires get hot,the resistance increases quite a bit--reduces the amount of current that can flow thru--and the current itself heats the wires up even more..a vicious cycle!..this reduces the amperage available to crank the motor over..it gets converted into heat,rather than making the starter crank over..
A battery that is on its last legs can harm a starter motor and other electrical devices..much like a "brownout" in AC current does..it can roast a starter motor by running it on lower voltage than it was designed for..and once they get toasted,the starter windings are permanently affected,and it'll never be at 100% efficiency again..
I am skeptical of the "remote" solenoid kits..the stock GM solenoid still has to pull the starter drive into the flexplate..all the "remote" solenoid does is give back a bit of voltage normally "lost" in all the wiring from the ignition switch,to the neutral saftey switch,that kicks the solenoid on the starter in.....
If you use a "short" solenoid off a later metric GM starter,along with a heat sheild,and make sure all the wires and connections are tight ,clean,and the wires themselves aren't all corroded,you'll likely get the same results as the remote solenoid gives....a dash mounted pushbotton wired directly from battery to the solenoid has cured even the most stubborn "hot start" problems I had in my 400 SB in one truck I had...its wiring was gangrene,and adding the pushbutton was much easier than replacing the harness..I used 10 ga wires to hook it up to avoid voltage drop..
