As president of the local astro society, I've had some recent dealings with a tower owner who wanted to build a new tower near our observatory. It has been quite enlightening to learn a little about this industry. For us, our concerns were with lighting, any tower 200' or taller needs nighttime lighting and appropriate daytime lighting or red/white painting. If a tower is under 200', it needs no lighting and can be painted any color or left bare gray steel. White strobes (which are aesthetically horrendous) are a cost saving measure, and it was fairly easy to get him to spend the extra money to install red filters.
In his case, all he does is own the tower and he rents space to other businesses. It's kind of like owning a communications strip mall. Thus, when asking why an existing tower won't do, this is one factor. It may be that a competing tower owner is looking for increased revenue.
As far as the actual design of the tower, there are many considerations.
- Most radio signals are strictly line of sight, thus taller towers allow a wider coverage area.
- While weight and space is a concern (antennas can be big and heavy), the biggest limiting factor on what can go on a tower is wind loading. This is another reason putting "branches" on towers makes no sense. They reduce the capacity for antennas, and may result in the need for additional towers!
I agree with DrWu, these fake trees are much uglier than basic towers. Simple towers with no lighting look like the best alternative for when a tower needs to be built. Chances are, we are not going to stop development, but we can work with the developers to minimize the impact.
Tony
Or maybe they can spray it with pine scent. 
