Something that most television viewers don't think a whole lot about is the fact that television content- the picture and sound- is really just data.  And just like old fashioned movies, even the most advanced television format consists of still pictures shown in quick succession to portray the illusion of movement.  Each one of these pictures is generally referred to as a frame, and at thirty frames shown on the screen every second, a movie or television program can contain tens if not hundreds of thousands of individual pictures.  When you think about how much memory it takes to store a digital photograph, and then multiply that by 100,000 for about an hour of programming you realize that the data requirements of modern <---****HYPERLINK****--->"http://www.newtechnologytv.com">television technology are truly staggering.
Unfortunately all methods of transmitting television programming have limited amounts of data that they can handle.  The amount of data a system can handle is called it's bandwidth.  Since each television channel requires a certain amount of bandwidth, most television service providers are limited in the number of channels that they can provide to their subscribers.  While this is true for both satellite television and cable television, the limits are more detrimental to the cable television industry.  Cables simply can't transmit as much data as the electromagnetic waves that satellite TV providers use.  <---****HYPERLINK****--->"http://www.newtechnologytv.com">Satellite TV providers are limited by the amount of the electromagnetic spectrum that's licensed to them to broadcast on.  The measurable difference between how many channels each can deliver is a result of the fact that the bandwidth licensed to a satellite TV provider is much larger than the typical bandwidth of the cables that any given cable TV company relies on.
There are two ways that both satellite TV companies and cable TV companies can go about increasing their bandwidth and thereby increasing the number of channels they can provide.  The first and most obvious one is to increase the bandwidth.  After all, if they have more data carrying capacity they can increase the amount of data they can transmit, and therefore increase the number of channels they can provide.
Unfortunately, this is easier said than done for both industries.  In the case of the cable industry, it means digging up older cables and replacing them with new ones that have a much higher bandwidth.  This seems like a good straight forward solution, but the downside of it is that the cables and the labor to install them both cost a lot of money.  Although it's a cost prohibitive process, the cable companies have decided to move forward with it anyway and finance the upgrades by increasing cable rates.
If anything increasing their total bandwidth is even more difficult for satellite TV providers.  There's only a limited part of the electromagnetic spectrum that's useful for telecommunications, and a much smaller portion of that is devoted to satellite television.  With the competition for electromagnetic bandwidth and the fact that the system for allocating bandwidth is governed by the Federal Communications Commission and international treaties (we're talking about outer space after all!), satellite TV providers are hard pressed to get more bandwidth.
Fortunately there is an answer for both industries in the form of data compression techniques.  The MPEG-2 protocol actually enabled the beginning of what we now think of as satellite TV by making Digital TV possible.  It also allowed cable companies to offer more channels than before over their existing infrastructure.  Now MPEG-4 makes it even easier to transmit more data, which opens the way for even more channels including ones in data intensive formats like HDTV.