Initiating a search involves using the return key on the keyboard. It's usual to have a corresponding button at the end of search bars for those who want to use the mouse.
An example where it could help: if I paste in a search term but then need to change the reference range, I must use the mouse. However, this then gives the focus to the range option. Pressing return on the keyboard does nothing; I must click back on the search term to give it the focus again then press return.
