According to TURTLE :

i work with all types of wire and some 4/0 or so

So do I, but not nearly as much as you.

and when it comes to a
#6 or #8 Al wire. they are real easy to work with. I would
never have thought about not being able to get Al wire at the warehouses.

Sometimes the pros forget the DIYer experience.

The typical DIYer rarely handles anything larger than #12 copper, and
will often find #8 copper a bit of a struggle, even when all they're
doing is direct connecting to screw terminals on stove/dryer receptacles
and pulling it through holes in studs and joists.

I remember my first exposure to pulling #8 Cu in a crawlspace well...
and not so fondly...

I shudder to think of what most DIYers will encounter trying to stuff 4
split-bolted, taped and gooped #6 Al splices into a regular-sized stove
receptacle box in a workmanlike manner. The technique and materials are
unfamiliar - they're simply not used to it.

Getting half of the wires down to #8 copper, and getting the cable a
little easier to pull is bound to make a significant difference for most
DIYers.[+]

Al isn't banned here ("prior approval only" on municipal permits). Yet,
I have yet to see _any_ DIY/builder warehouse[*] or hardware store
stocking #6 Al here - indeed, _any_ size Al for that matter... While
there probably are places here where you can get the cut lengths from
rolls here, it'd be special order even in most electrical supply
outlets.

For the most part, Al use is limited to electricians wiring lots of
houses, where the cost savings (buying multiple rolls) makes a
significant difference. For a homeowner extending a circuit a dozen
feet or two, a few bucks difference (at best) isn't going to make up for
the inconvenience of finding the stuff and installing it. You may
find you spend more money on gas just getting the stuff.

[+] while of course this is somewhat larger, when my professional
electrician friend installed a #4-#3 copper-Al splice for my 100A subpanel
feed, the box he used was at least 3"x4"x6" - 2-3 times the volume of a
typical stove receptacle box. From what I call from observing him, I
wouldn't have wanted to try anything smaller myself, tho, he could have
managed it I'm sure. [The splice was because the ganged 100A breaker he
gave me from his "used parts box" wasn't rated for Al, but using Al for
the 120' feed saved something like $200 over copper.]
[*] Ie: HomeDepot or Rona (Rona is HD's primary competition in Canada).
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.