keep ...-ing, have been ...-ing, leaving (something) on, leaving (something) still in use
Verb ます stem +
This grammar point is used to describe a situation where an action continues for a long time, or more commonly, where something is left in an improper or messy state after an action has been performed. It often carries a negative nuance, suggesting that the person should have finished the action or cleaned up afterward.
Continuous Action
When used with verbs of movement or continuous action, it indicates that the state or action has continued uninterrupted for a duration of time.
一日中立ち
I have been standing all day.
彼は一時間もしゃべり
He kept talking for an hour.
Improper State
This usage emphasizes that an action was performed but the resulting state was not properly dealt with or closed. It expresses that something is 'left as is' in an undesirable way.
テレビをつけ
You left the TV on.
ドアを開け
Don't leave the door open.
水が出
The water was left running.
While this can sometimes mean simply 'continuing to do something' (like standing for a long time), it is most frequently used to complain about someone leaving things in an unfinished or messy state. It is informal and should be avoided in very polite settings.