Sure, estimates are, well, estimated... based on what the
person estimating knows at a point in time, the choices are (1) I estimate it
it will require "X" to do it, or (2) I can't estimate what is
required to do it. I think this comes down to people not wanting to accept that
an estimate could be wrong, or not right enough.
I get an estimate when I need car repairs, to make sure I
can or want to afford it. My mechanic calls me when he finds something he did't
know that will change the estimate, and I decide what to do. If I find over
time that my mechanic always under-estimates the cost, eventually I will change
mechanics. The average reality should be a bell curve around an estimated
value, an estimate is almost never exact, but a
statistically acceptable variation is what you should look for.
Now, such analogies
of physical things are problematic when used to describe an aspect of software
development. Software is intangible for one thing, and we really haven't been
creating it very long to have some good tools like other disciplines (like
Engineering) for predicting outcomes; but like everything else, it takes time
and money to create it, so the people investing that time and money usually
want an idea of how much that investment will be to get what they need. Just
saying an estimate is worthless isn't really going to go over well.
The advantage of
software over physical things is that you can indeed create small amounts of it
that can be seen to work. Long before 'agile' got its name, a lot of software
projects switched from estimates to
time-boxing: give me x amount of resources and the project will deliver what it
can in that 'box'. Investor spends a little to see what he can get for that
amount. If it looks good, run another time-box. If it doesn't look good, you can
stop with only a small investment amount having been spent.
Lastly I would
comment on your statement on what does an estimate have to do with creating
good software and a good return on investment. ROI is a funny thing, often very
date-specific; delivering great software after a competitor has already done it
and captured the market will kill your ROI. Some windows of opportunity are
very short; miss them and the return is nil. In these cases, you have to have
some way of knowing if you can make the window. Like it or not, an estimate is
one way of trying to figure that out. It is these kinds of situations that will make investors
wary of new development and look for packages or services to meet the need.
Nothing is perfect but not being to
estimate software development may just lead to no new software being developed.