Relays are expensive and have limited lifetime. Choosing a proper relay for a particular application is also important. In other words relays require a bit more of everything when compared to a simple electric switch. So why not instead of using relays, manufacturers somehow couple a small servo to a simple electric switch. Then use it for switching, by controlling the servo. We too can do it (though not perfectly) . What's the reason that relays are so popular and so common for power switching? What's the flaw in using a switch as suggested?
Edit: Using switch can be a one time investment instead of using relays which requires replacement. Also, the cheapest servo motor(premade) can do the work for us. Main idea is lifetime, which I think, may be a reason enough! Also, if this setup is fabricated there may be less chances of individual part failures.
Best Answer
That's what a relay is.
In both cases you have a set of contacts carrying current. In both cases there is a mechanism for moving the switch: in a relay, this is done by a magnetic coil. All techniques available for switch construction can also be applied to relay contacts.
The lifetime issue is only visible on relays because they generally get switched a lot more often than humans can manage on a switch. If you look at lifetime specs in terms of number of operations they're usually similar.