Yes. It makes sense, particularly if you use a variety of boards/equipment (e.g., TT, foilboard, directional). As wind and/or water conditions change, board choices change, and so too do kite types/sizes/shapes.
I have a quiver of LEIs that I use for TT, but I almost always use a foil kite when riding my hydrofoil. On a directional, I prefer an LEI with more drift than those I use for the TT. I think a lot of people (particularly those who have accumulated lots of kites over the years) do something similar.
Now, if you're asking about buying a variety of kite types/shapes for a single board type (e.g., TT), it may not be as "essential" because most people tend to gravitate towards a single style of riding on a TT and, therefore, invest in a quiver of similar kites in different sizes to support their chosen style. But if, unlike others, you want to ride a variety of TT styles (airstyle, wakestyle, waves, etc.), then different types of kites in your quiver would be useful.
Bottom line: if more types of kites = more fun for you, then do it.