It depends
It depends on why that particular individual joined the reserve component.
A lot of people coming off active duty not understanding the pay system, think they want full time jobs for the security. But they really torque the leadership if they sold them on why they should hired full time, without revealing intentions to seek airline employment. It takes a hard sell to walk into a full time slot from outside the unit, and they must really need somebody to fill that slot if they are willing to take an outsider. So using that job to hold you over, then blindsiding the leadership with two weeks notice after obtaining an airline job is not cool.
Some people like what they did on active duty and want full time jobs, but don't what to move anymore so a full time reserve job offers that.
Some people take military leave after they get hired by an airline and finish probation for a 3 year full time AGR(Active Guard Reserve) tour with the reserves, because they make more money at their current military salary than the first couple of years at their company. They go back to their company with a better schedule due to higher seniority, equal or better pay, and did not sacrifice as much precious family time.
There are people who like the traditional reserve position. They can run their own business, if they are not airline guys. They love military flying and aren't ready to give it up, but want to do something else in life. Unemployed guys seeking employment can control their lives while spending time with the family, but keep current in flying and pay the bills. (I am currently on a six week vacation to do spring chores and spend time with the family) A flyer can make 75% take home (with per deim from TDYs included, if they don't spend it all) of what a person on active duty at the same rank makes just in regular pay with no TDYs. Personally, I budget plan for 50%, so I don't extend myself or get into a position of really needing that last trip that always seemed to get cancelled.
Some of this depends on family situations. People with families need health care. If their spouse doesn't work or get a good health plan through his/her job, then they desire the full time slots, because those off the shelf family care plans can be quite expensive.
Lastly, it depends a lot on the job market. Now, there aren't too many full time jobs available. When the market bounces back, there won't be as many people seeking those slots.
Government/Military service is nothing but welfare for the educated.