There is no such thing as too many options. Choice is good. Having no choice
is bad. Not being able to weigh the options is perhaps bad, but you are not
put in that situation because Ubuntu comes with one desktop, as does
Kubuntu, Xubuntu, Lubuntu, etc.

Yes all can be installed via Synaptic.

Each desktop environment has its own niche. GNOME that comes with Ubuntu and
KDE that comes with Kubuntu are full blown desktop environments that can go
toe to toe. But XFCE which comes with Xubuntu offers less but not by much.
It also consumes fewer resources, but it has become a lot bigger over the
years and there is little to distinguish it from GNOME. All applications
that will run in KDE or GNOME will also run in XFCE.

As XFCE has grown, it has made less resource hungry desktop environments
more popular. LXDE that comes with Lubuntu has developed a loyal following.
It runs on hardware that would be taxed by GNOME. Fluxbox and Openbox also
fit into this category.

The problem arises that people with low end hardware want to run what others
do and this is often not the case despite having a light desktop environment
because the application such as OpenOffice has resource requirements of its
own that put it out of reach. Running with low specs means that the user
must be willing to compromise as in some cases this means using an
application such as Abiword instead of OpenOffice. I am amazed how many
people think that they can do what others do while using Puppy just because
it uses less and fail to think that their processor or RAM just does not cut
the mustard no matter what desktop environment they are using. That is why
lower resource desktop environments come with Abiword instead of OpenOffice.
The developer is being realistic where users frequently aren't.

We have choice so that people can tailor the environment for their own
systems. There is no sense for me to be running LXDE when KDE 4 works just
fine. I am limiting myself and unless that is my intention is seems absurd.
But I am free to do so if I want. That is what Linux is about. It empowers
users to do and try anything that they want. The results may not always be
good, but you can tinker under the hood to your heart's content. Life is
good!