Letting offers languish unanswered is either used actively to let people feel a sense of anxiety, or passively to signal non-interest at the current time. If you are approached after time has passed, it is likely there is high interest. This process tactic is a result of not letting persons know what timeframe is expected.
An offer is made on a device, and nothing happens. Then, suddenly, the seller must close immediately.
Set your expectations at the front or end of the negotiation, “I will hear from you by Tuesday?” For formal negotiations, you may want to be very specific: “Please reply to this letter no later than 9:00 a.m. PST on October 15, 2019.”