If I didn't have as many tanks as I do, I'd spend a great deal of my time every day between the kitchen sink and the toaster oven to wash and dry my tanks and coils. I may be somewhat weird in my vaping but I like to change my flavors throughout the day, some days I might go through as many as 5 or more flavors, there are of course times that i'll vape one flavor for weeks on end and the rest of my tanks sit in their holes in my desk waiting for me to revisit them but in general I pop different tanks on my batteries every couple hours for a different experience in flavor.
So, it's not weird to me but may be to somebody that only vapes one flavored liquid for months or years on end.
It's just downright convenient to already have a tank filled with the liquid you want to vape. I tried to make it easy using a dripper once but to be honest, even if I'm only changing out the wick on the dripper, it's faster for me to simply spin off a tank and spin on another one, not to mention a lot less mess too when trying to do it while stopped at a red traffic light.
Some of my tanks though were bought on the road to finding tanks that I'd actually like using and don't get much if any use anymore but that still leaves me with too many tanks that I'm constantly switching out during the day. When I go out, I don't wonder what tie will go with my outfit, but rather what flavors I might want to vape today and grab those tanks on the way out the door.