One should not simply slap down some mastic (glue) or thinset (mortar) and put tiles on it.  

Every installation is unique requiring expertise as to the specific substrate and fixing component. Not to mention taking into consideration of various tile sizes, and quality of the tile and cost to install tile.

Tile quality and length greatly effects the installation due to cupping or a bow in the tile as manufacturers force the kiln process to produce greater quantities of tile. This means the tile setter must compensate by using a recommended pattern to prevent lipage (tripping points or uneven tile heights).

Over the years we have seen many people spend as little as $1500 and as much as $50,000 on small jobs to entire homes, to find that the “contractor who also does tile” was not his expertise. 

Face it, you don’t call a plumber to install an electrical panel, or a painter to install a hardwood floor and you surely don’t go to a general practitioner MD for major surgery, so why hire a handyman to do tile?