Rokeach Siddur

What is the reason of appearance of Siddur Sefat-Yisrael? Why not to fully accept Rokeach's Siddur? He is also from Mainz and follow Nusach benei-Ashkenaz! His Siddur differs from modern day Siddurim slightly. Why Yekkes don't use Rokeach's Siddur?

As far as I know, KAYJ, and MMA in general, follow Minhag Frankfurt. The Roke'ach followed Minhag Mainz. Furthermore, it is unlikely that today's editions follow the nusach of the Roke'ach, as many publishers prefer to use mainstream siddurim for the nusach (see also the Siddur of the Ya'avetz, which is often printed in Nusach Sefard and includes passages from the Zohar, which R' Yaakov opposed).