hypocricy

Question

i have found many bochurim in EY that will only eat badatz (at home) but can still go to people's homes on shabbos who aren't neccessarily makpid is there any such svarah ( i was thinking that while seated at the table the food is brought out and "KOL DEPARUSH MERUBA PARUSH as opposed to bringing to your house it's KAVUA, yah i didn't think so) another quick q .if you have a maid at home do you have to turn on the fire or is home different thank you