It is not compulsory to use the TLM Analysis FIFO's. But it is recomended way to use these FIFO's.
As the Moniotor's and Scoreboard are used for analysis of the data. These components should not block the current simulation time. If we use normal FIFO's(TLM FIFO's Which have limited size), if FIFO is full it can't store the data and as it is blocking statement, it will wait for FIFO to be free. This will waste some simulation cycles. If we have TLM Analysis FIFO's which have infinite size, always we will have memory for the transaction formed and no simulation cycles will be wasted. So it is better to use TLM Analysis FIFO in Analysis part.