Tea strainer in the shape of a teapot with a drip tray. Although the modern fine mesh tea infusers are mainly replacing tea strainers there are still some reasons to use the old fashioned device.
If you are brewing tea in a teapot and intend to pour out all the tea at once there is no problem with over brewing. Putting the tea directly into the teapot gives it more space for the loose leaf teas to open up, expand and "swim" around the teapot. The Brown Betty teapot was an innovation when it was first introduced in the nineteenth century as it allowed the tea to flow around the circular diameter that did not happen so well in the rectangular or square teapots of the time.
It is perhaps considered more elegant to pour the tea through a strainer in a dining room situation than taking out a dripping infuser or waiting for the tea to brew and take out the infuser in the kitchen.
There are also now many different attractive shapes of strainers that are fairly inexpensive in comparison to the silver types of past years.