I second the comment about the more expensive rooms having more space.
Also, some resorts are set up so that you will be able to park your ECV in the hallway overnight and even recharge it. I found at the Animal Kingdom Villas (Kidani side) the room doors were set back a little bit from the hallway in sets of 2 with enough space between them so I could park my ECV without blocking either my door or the neighbor's door. There was still plenty of room in the hallway for people (as well as maid carts) to get by. I always took the ECV key with me and left nothing in the basket, but no one ever messed with it even though I left it plugged in overnight to recharge.
You are responsible for the ECV, and expected to keep it in your room when you are in your room.
Cast Members can - and will - move the ECV if they believe it to be causing an obstruction of traffic, or a potential traffic issue. (This is true of anywhere on property - just like they are often moved at the Theme Parks for traffic purposes.)
Additionally, you might want to price out the replacement cost for that ECV before you leave it unattended overnight - if it is stolen, or "misplaced" you may be on the hook to the rental company for full replacement cost; check the fine print in your rental agreement.
Just because you don't want the ECV in your room doesn't mean you are allowed to park it in the hallways and it's not just about the width of the hallways, or your opinion of whether or not an obstruction is/has been created.
It's about leaving a high-ticket item unattended in a public space, where it could potentially cause a traffic flow issue. I double-dog dare you to call any Fire Marshall in this country and ask *their* opinion. They are going to tell you that it either has to be in the room (and not blocking the door) or in a specially designated area (which Disney does not provide, because you are supposed to park it in the Resort room.)
It's about leaving the very piece of equipment that you are relying upon to be your legs at WDW out of your control all night long. What if someone comes along in the middle of the night, and unplugs it? You will spend the next day constantly searching for outlets in the Parks instead of having fun. That, BTW is the best case scenario. They could also move it - down the hall, or to another floor or building, or even push it into the pool. They could hide it in a Guest room, and until the Resort was searched, room-by-room, no one would know where it was. (This, as an aside, is why WDW is smart not to allow Guests to use bell carts without a bellman; during the last convention I worked as an event planner, the hotel we were based out of told me that all of the bell carts kept disappearing, and housekeeping would find them - sometimes even "hidden" in the bathtubs, with the shower curtain pulled closed. No kidding. People would also steal housekeeping carts and courtesy wheelchairs, and hide them in their rooms as well. Things like that are why event planners and wedding coordinators are always on the verge of a nervous breakdown)
Yes, WDW *is* a safe place - the vast majority of Guests there never have a problem with the security of our personal items. But that doesn't mean that it can't happen... and leaving an item like a scooter unattended all night could pose an opportunity for mischief that needn't have happened.
It's about being an adult, and taking responsibility for this piece of equipment. Yes, we all come to WDW to live inside the "bubble" for a few days, and escape reality, but that does not mean that we can just ignore our basic adult responsibilities.
Sometimes, doing what is right takes a bit more time or trouble than what is easy. Please do the right thing, every time. We have enough folks in the world who try to take the easy way out.