Has anyone noticed (is it just this field?) that you can make more money by switching companies then waiting for a raise

example:
woking at commerical HVAC outfit (just starting in the trade) ended at $12.00/hr after 1 year, started at $10/hr

then my apt. complex offered me a job as a maintenance tech, not really stimulating work but $14.00/hr and 1/2 off my rent

got accepted for a maintenance position for a chain of restaurants. learn more about refrigeration, but after a year all the equipment is the same setup so nothing new anymore. Just HVAC work on the roof, fixing coolers/freezers not very stimulating anymore, oh and the cooking equipment isn't complex (not our stuff anyway, just grills/ovens/fryers/stupid microwaves)

anyway started at $16.00 franchise owner said no raises this year (economy was the reason)
but the pay is decent, sometimes dosen't seems to be be inline with the workload
free meals (but it makes me fat, gotta start bagging it again), truck, good insurance, but i WORK ALONE (annoying as hell never having anyone to bs with)

just seems that when you try to reason with your employer raises seem to be a quarter here or there, but they are just too quick to let you leave.

sad but maybe its just me that these job all seemed to last 1 to 2 years, i seem to be bored easy i guess, and no im not saying im a master tech (far from it) but does anyone else get bored with working on the same equipment day in and day out. I would like to get back to commercial just for this reason, from pkg units to splits, vav systems, and chillers (the last two i unforuntly never got much experience with)

maybe im just trying to justify my rambling lol