*Talking from a patient's perspective here:

Because patients find them very comfortable, provide excellent vision,
and they are widely available.  Extended contact lens "abusers" like
them because they eye generally remains comfortable up until the point
CLARE or bacterial keratitis kicks in.  Patients generally don't like
lenses that "tell" or "remind" them that they are abusing themselves.

Also, some patients are extremely cost conscious.  When I have tried
different contact lenses in the past to try and keep him up with
modern technology and contact lens advancements, his first question is
always whether these lenses can be obtained at CostCo.  This same
patient just last week that to stick with his Acuvue2 over Oasys
because of the $5-$10/box difference.  I thoroughly educated him about
the advantages of silicone hydrogel contacts, but he is motivated
primarily by price rather than what is best for his eyes.  I moved him
to Advance a couple years ago, but he went back to Acuvue2 the
following year because they were $5/box cheaper at CostCo.

He wears the lenses on a daily wear basis (albeit stretching them out
to last about 3 weeks against my recommendations) and has no obvious
contact lens related complications, so ethically it would not be right
for me to insist he wears what is best rather than what which is
adequate.

*Talking from an OD's perspective here:

I think Acuvue were great lenses for the time, just like gentamicin
was great at the time for bacterial keratitis.  Now, it is old,
outdated and deprecated technology.  For me, Acuvue (and other
standard HEMA disposable SCLs) are never a first choice, but rather
one of the last choices.

Prior to silicone hydrogels, ODs just "accepted" a certain amount of
microcystic edema and limbal neovascularization.  In 6/2006, there is
almost never a reason to put up with those contact lens related
problems.

Likwise, I prefer to prescribe silicone hydrogels as much as possible.
For essentially spherical patients, I tend to prescribe CibaVision's
Focus Night & Day for people who insist on wearing the lenses between
7 and 30 days of EW.  For <7d of EW, I tend to use Ciba's O2Optix and
Acuvue's Oasys (I like these lenses but the 8.4 BC limits my use to
steeper corneas).  For daily wear, I use a mix of O2Optix, Advance and
Oasys.  I used PureVision a lot in the past, but I stopped using them
during the period they were off the US market and never started up
again once they came back (that and the fact that my B&L rep is a
major flake).

And daily disposables have a good place for selected patients.

Certainly.

I generally stick to a certain core group of lenses so I can be
thoroughly familiar with them -- know how they work, feel,
complications, idiosyncracies, etc.

And I don't do a lot of experimentation, unless a certain type of
contact lenses promises real benefits.

There were a lot of soft contact lens materials that made a lot of
promises (in between HEMA and silicon hydrogels), but I think the only
one that really lived up to the promises were the Proclears.