I am the SCCM administrator for my company, and I can tell you that I never use SCCM task sequences to capture an image. I still do it the "old-fashioned" way.
I prep the reference PC the way I want it, create an answer file, sysprep it, and capture a WIM. Then from the Operating Systems Images node in SCCM, I import that WIM file and base my task sequences on it. When I create the task sequence, I specifically check the box "This task sequence will never be used to capture an image."
So to answer your question, no you're not missing anything. SCCM just provides an automated way of capturing images, but there is no requirement that you use it. If the method you have always used is comfortable for you, you can continue to do it that way.