Why does everyone not mine bitcoins?

There simply isn't enough time to go into all the whys... In April, Bitcoin blew up. It was about that time that you had several companies announce new mining hardware like ASICs that were designed for the specific purpose of mining. Since that time, it seems that there is a race to own the most hardware. Move forward to present day and we have several companies producing the hardware, and even several companies buying datacenter's worth. All this new mining hardware has introduced a HUGE amount of processing power.

With the added computational power, the bitcoin block difficulty has gone up exponentially. (see my attached image)..

As it becomes more difficult to find a block, the payouts on your same hardware come around less and less (It takes longer to find a block and receive the 25 BTC reward) causing you to have to constantly buy more hardware to maintain. Add into this the power costs of running miners, and MOST people find that they are spinning their wheels.

Can you buy tens of thousands in new hardware and keep up? Adding new (latest) hardware will never stop if you want to maintain mining levels and you are getting a VERY late start. Most of the large centers already have a HW provider relationship and orders in the books.

So, I doubt it. That's about as quick and easy as I can lay it out...

Side notes:

The piece of hardware that you are asking about, my best guess is you are talking about Butterfly Labs. You should probably stay VERY far away from that company. They are still trying to make good on presale orders from LAST MARCH ORDERS. If you believe they will have that new item ready for market, you should do a little research about the company and how many people are pissed off at them around the webs.

There is also the possibility that you may find cloud hashing interesting. This is where someone else owns the data center, and power, you just lease the mining. Good luck.