Ceramic tile over ceramic tile

I have an entry way/kitchen area with ceramic tile that is about 25
years old. Tile is on concrete and is in perfect shape, other than
being really ugly.

I have read in two tile books that if your tile is in good shape, that
you can tile over it with the right preparation. The current tiles are
8"x8" and I want to lay 16"x16".

The reason I question what I have read is because two neighbors that
have had pros do their tile both removed the original tile. I do know
that one had a history of cracks and is on their 3rd floor. Could it
also be that the contractors simply want to creat a larger job for
themselves?

Any thoughts on tile over tile/concrete if the original is in great
shape and I'll be using larger tiles - ie crossing over 4 tiles.

Thanks for your thoughts,
Don