A comment to this question raised a point I always found weird as well:
Why would Skynet send back one terminator to 1984, one to 1992 and three hundred terminators to 2007? That was never explained.
Answers only bases in canon please, no guesses.
A comment to this question raised a point I always found weird as well:
Why would Skynet send back one terminator to 1984, one to 1992 and three hundred terminators to 2007? That was never explained.
Answers only bases in canon please, no guesses.
So, using another answer as a source, there weren't nearly that many in SCC. The focus of the movies and the series are different, so it had more range of freedom in exploring the world - when on the run as in the movies, there isn't nearly as much time to go on the offensive, as they did in the series. (And I mean "offensive" in terms of stopping Skynet from being formed, not in attacking the Terminator currently after them)
Sarah Connor Chronicles, Season 1
Sarah Connor Chronicles, Season 2
From this list, we only have 3 terminators that are known to have an objective involving John Connor, and a couple more that might have encountered the Connors.
One of the key differences in the Sarah Connor Chronicles from the movies is that they're no longer simply on the run from the Terminator currently after them - thanks to the time jump forward in the first episode, Cameron gave them freedom and, because she wasn't destroyed in the process, was able to impart some extra knowledge that allowed them to go on the offensive. Most of these Terminators would not have been encountered if they were still in a purely defensive "save John Connor" mindset.
Also mentioned in the series is that both Skynet and the Resistance are sending people all throughout the past century or so in an attempt to shift the timeline in their favor. If you accept SCC as canon (rather than solely T-3), it's fully possible that Skynet was sending Terminators into the past during the events of T-1 and T-2, but because the focus of those movies was on protecting John Connor, it just never came up.
So 3ish Terminators being sent to kill John Connor still seems rather high, right? Well, not quite:
9 years is a fairly decent gap.
My theory is that Skynet learned that playing with time travel could be dangerous for itself and alter is development.
Skynet's creation was dangerously compromised by the chain of event of Terminator 2. Sure, sending the first Terminator boosted it's development with the research made by Cyberdyne Systems on the salvaged chip. But, is the Skynet resulting from this time-line the same as the original one? Probably not.
Skynet figured that out by the time it reach T:SCC timeline, so it decided to avoid to interfere with it's own development. However, it judged sending Terminators back in 2007 didn't affect his development since it was too advanced to be significantly changed.
I'm sorry but there doesn't seem to be a real canon reason for this. Either time travel and terminators are readily available or they are so rare that they must be used only for vital missions. The two apporaches don't line up without a big fudge.
We know the real reason is that there's a difference between movies and TV shows so we'll just have to put up with this as it stands.