Recently, I saw this "hack" of attaching a blender base to a canning jar. This works for most blenders, but not all of them. (Side note: I absolutely hate when I see "life hacks" on Facebook. I do not want any part of my life hacked, it sounds awful. And don't get me started on the videos of "You've been doing ____ wrong". No I haven't been doing it wrong. I've successfully cut cake and watermelon up to this point in my life, it's not wrong!)
Rant over. Back to my smoothies. As silly as this sounds, sometimes I don't want to make them in the mornings because of extra dishes. If the sink is really full, a bowl of oatmeal will only dirty one dish, whereas a smoothie will dirty two: the cup I drink out of and the blender. The oatmeal wins.
I needed a new gasket anyhow for my blender after I didn't put it back on correctly and it shredded into pieces, so I got a new one in a pack with a whole new blender base. Now I have two blender bases--woo hoo! It's much easier to clean just the base and the jar instead of the whole blender and my cup, and I'm all about less dishes.
My immersion blender in a canning jar also works well and I've started using that some too. It worked really well and still left me with less dishes than a regular blender.