Some people are actually proud of their patents, even in CS area. I was pretty surprised about it, but someone I know was really happy that they got their 13th patent granted.
To summarize, do not confuse bad cases from good cases. You cannot have a blanket statement of the type, "some people are proud of their open-source contributions ... I was surprised about it".
My understanding is that before patents, people and companies would invent but keep their invention a trade secret for as long as they can, which meant they had exclusivity to the invention. Patents allow such exclusivity for a limited period of time in exchange of disclosing the invention and losing rights over it after a specified period.
The patents applicability criterion correspondingly includes non-obviousness which is to judge if someone else could come up with the same invention without investing significant time and effort or not. Majority of the ideas are "supposed to be" ruled out by this criterion.
The state of the affairs however is that most obvious of the things get patented because (1) obviousness is unmeasurable, and (2) searching the prior art fully is impractical.
Short message: You cannot call all swans white simply because most you see are white.
The truth is, the vast majority of software engineers don't even know what a patent is. Of the rest, some are neutral, some are pro-, and some are anti-software patent. Of course, you only ever hear from the latter group because they think it's a big problem, and the rest really don't see anything wrong.
Same reason that I don't vote. I think a lot of people fall into this category of thinking.