If you take a different example, say, improvements to JPEG, it's a lot harder for camera manufacturers to ignore patents. You're at the mercy of the patent holders, whose terms apparently haven't been reasonable enough for anybody to improve the compression in digital photos beyond what we had decades ago.
When the people who spread adoption ignore the law, sure patents don't prevent anything, e.g. https://en.wikipedia.org/wiki/MP3#Internet_distribution
If you take a different example, say, improvements to JPEG, it's a lot harder for camera manufacturers to ignore patents. You're at the mercy of the patent holders, whose terms apparently haven't been reasonable enough for anybody to improve the compression in digital photos beyond what we had decades ago.