I got the 75F pitching temp from my local home brew store's directions.
I see that a lot and I don’t like it. Just last night I was asked to double check a HBS’ directions for making a lager which asked for pitching at 75 F (!!!!).
To understand this you have to keep in mind that a HBS’ primary objective is to make the process simple and avoid calls from angry customers when they don’t see fermentation within a day or so. They also look for a method that allows pitching a beer w/o the use of a yeast starter.
But many experienced brewers will tell you that your beer will be better if you ferment slightly on the cool side for the yeast (65-68F for ale and 48-50 for lager) and pitch a few degrees cooler than the fermentation temp. This allows the yeast to get up to speed more gently and they won’t produce as much esters and , which is most importantly, fusels. But to make this happen with a reasonable lag time and fermentation performance you need to pitch more yeast than there is in a vial or smack pack. This is in particular true for lagers. Here is where starters come into play. They are mini fermentations aimed at vitalizing and possibly multiplying the yeast.
You may also use dry yeast where you don’t have to make a starter.