In altera Transceiver, why some protocols need rate match fifo, some don't need?

sysysy,

unless you were to use the recovered slow clock as base for _everything else_ in your design, you'll have to, at some point cross, cross between the recovered slow clock domain and another (local) clock domain.

Unless these two clocks trace back to the exact same crystal, they'll drift: one of them will inevitably be a bit faster than the other and periodically you'll be short of data or in excess of data.

You need some kind of elastic scheme to deal with this. That's the job done by the rate matching FIFO.

In some applications (ie, SRIO) it's mandatory that all endpoints trace their reference clocks back to the same source (same crystal).

In this case, there is no drift and the rate matching FIFO is not needed.