Anyone who owns a Nintendo 3DS will notice that the technology associated with the touchscreen is identical to that of the Nintendo DS, a device which came out seven years prior. But according to Nintendo, they purposely chose not to improve it.
According to Hideki Konno, a hardware producer on the 3DS, it was about backwards compatibility issues. "Really, it's all about the backwards compatibility," he said during an E3 interview. "We have to play DS games on this and we want to make sure they work."
Nintendo felt that if they enhanced the tech, they couldn't guarantee that Nintendo DS games would still work properly, so they decided to just stick with the DS' touchscreen tech.