Because the red cross has been used for centuries, as well as the red crescent, to symbolise "the service to humanity", usually in medicine. You may notice that hospitals also use red crosses.
The Red Cross charity named themselves after this famous cross.
Contrary to popular belief, the red cross did not originate from Christianity, which also uses the cross as the official symbol. There is a difference between a cross and a crucifix (a crucifix is not a true cross).
Centuries ago, every single nation had a symbol to identify their military. Different shapes were used on the shields and uniforms of different armies, such as diamonds, squares, triangles and crosses.
The European military were generally identified by a red cross on their uniforms and shields. When they set up mobile hospitals in countries they visited or conquered, the people would recognise the red crosses as a symbol of help, particularly medical help.
So, in summary, red crosses came from military uniforms, not Christianity.
See the related link below.
The white cross on a red square is the swatch logo
Thai Red Cross Society was created in 1893.
Swatch
no there isnt
Nepal Red Cross Society was created in 1963.
Lao Red Cross Society was created in 1955.
Cameroon Red Cross Society was created in 1960.
Lithuanian Red Cross Society was created in 2000.
Tonga Red Cross Society was created in 1961.
Zimbabwe Red Cross Society was created in 1981.
Kiribati Red Cross Society was created in 1965.
Samoa Red Cross Society was created in 1934.