Exact quote:
"By clicking "I agree", by installing the product, or by accessing or using the product or other software, if any, provided to you on the package, you acknowledge that you have read all of the terms and conditions of this agreement, understand them, and agree to be legally bound by them"
You are right that making the customer click an "agreement" button before installation is the best way to make sure the EULA can be upheld. If simply installing the software automatically placed you in agreement then there are some courts that might over rule the EULA in those cases. I don't remember if Skyrim required an acceptance click before installation on my PS3 or not, but I would be shocked if there wasn't because it's a pretty easy legal 'safeguard'.
I'm pretty positive there is an acceptance click, which means skyrim could in face enforce their EULA, at least moderately(I know several people who fought the EULA that Squeenix used in conjunction with FFXI, and they(They being Squeenix) lost miserably, it was a guy on Allakhazam forums from over in the U.K. He got every bit of information he was pursuing them for, and even posted it and the legal document he got stating he had won the case and the judges ruling and specification as to why). So, while a EULA can be enforced, it doesn't necessarily mean it WILL be enforced, and in the case of no clicking "I accept", which is almost always the case with console games, it would add that much more weight to any actual legal proceedings. There is a lot of difference between theoretical, and actual application. EULAs are mostly a scare tactic to ward off 90% of cases, but the people who are really serious about going against them, often get it to court and win.