It's not so much the sanctification, as it is the absolution of sin.
If I am free of sin, I am "saved." When I sin anew, I must repent and receive absolution.
When I sin, I have wronged God and others. To me, the idea that I got "saved" 4 years ago (for example) and that therefore when I sin, I have already repented of it and already been given absolution is nonsense. When I harm God or others, I need to repent. I can't just point back to one point years ago and say "I repented then and got forgiveness."
It is this "cart-before-the-horse" method that makes Protestantism a non-starter for me. I can understand that I am forgiven and will be forgiven when I sin. But there is a human need to address sin periodically and on an ongoing basis that I feel.
If I haven't even done the sin yet, there is no way I can atone for it.
SD