A couple of factors at play, I suspect. In my area I may do a lot of work for one company one year and the next year either the client is gone, I am finally out of rotation for most shops they offer or they just start assigning the shops to a 'fresh pair of eyes' on the assumption that that is in the best interests of the client. The other day I got a 1099 from a company I had done virtually nothing for in 5 years, yet the latter half of 2015 we 'reconnected' in a big way. It would appear that I will be doing about $125-$150 per month or more for them in 2016. Another company that will be sending me a 1099 has done so for a number of years, but I have grown bored and blasé about their jobs. 2016 is unlikely to be a 1099 year unless they pull some fresh clients out of the woodwork.
What I am saying is that 'favorite' companies come and go. If you aren't seeing enough work you do need to register with more. If you are bored with what you are seeing you need to register and check with more. If you are in an area where you were seeing 20-30 jobs per week with just a couple of companies it is very likely that lots of other companies have shops in your area as well.
just when I am building and finally learning the MSC trade.