Hi Jimmy, are you talking to Trulia or to brokerage firms? Since Trulia is a public website where anyone can even just SAY they're an agent, I'll move on to brokerage firms.
Agents are independent contractors, they are not employed by the place where they hang their license, they are self employed. An agent may work as a Realtor and then find the need to get a salaried job and want to keep their license, too. After all, contrary to what some people in the public may think, it does take work and expense to obtain and retain a license, so even though someone may have to take a salaried job out of necessity, or have to take a leave of absence from real estate in order to raise a child, they still keep their license. As for asking the broker why they keep them, well, why not? The agent may list a relative's or neighbor's home, and they will still be bringing money in.
Now that I have answered your questino to the best of my ability, I have some questions for you also (based on my years here I know I will probably not get an answer, but I may be pleasantly surprised).
What is your reason for asking this question Jimmy? How could this affect you? Has it created a problem for you?