Inertia
Also known as: Behavioral inertia, Status quo inertia
People tend to stay on the current path simply because changing takes effort and intention.
What it means
Inertia, in behavioral terms, is the tendency to remain in one's current state or continue a current course of action through inaction, sticking with whatever requires no decision rather than actively switching. It is closely related to but distinct from status quo bias: where status quo bias emphasizes a preference for the existing option, inertia emphasizes the role of passive non-action, procrastination, and the cost or hassle of doing anything at all, so people stay put even when they mildly prefer an alternative. The forces behind it include the effort and attention a change demands, present bias that postpones the bother to later, anticipated regret from active mistakes, and the implied endorsement of whatever is already in place. Inertia is what makes defaults so powerful: because changing requires effort and a deliberate choice, most people accept whatever is pre-set, whether an organ-donation status, a savings-plan contribution rate, or a subscription that quietly renews. It matters because designers can move large-scale behavior simply by changing what happens when people do nothing.
Examples
Enrollment in workplace retirement plans jumps dramatically when employees are automatically enrolled and must opt out, because inertia keeps most of them in.
A streaming subscription you stopped watching in spring is still billing you in autumn: cancelling takes four minutes, and every month you decide to do it next month.
Most households never switch energy supplier even when a cheaper tariff is one form away, so they pay a loyalty penalty for years by doing nothing at all.