Siddur Ashkenaz, Weekday, Shacharit, Preparatory Prayers, Torah Study 4:
אֵלּוּ דְבָרִים שֶׁאָדָם אוכֵל פֵּרותֵיהֶם בָּעולָם הַזֶּה וְהַקֶּרֶן קַיֶּמֶת לו לָעולָם הַבָּא. וְאֵלּוּ הֵן...וְעִיּוּן תפילה.
These are the items for which a person eats the fruits (of his labor) in this world, but the reward is established for him in the world to come ... study of prayer.
I have seen very few places emphasizing the study of prayers - the origin, history, reasoning of why prayers are said, meaning of the words, etc. I'm not stating that individuals may not do this, but when I was in yeshiva elementary and high school, there wasn't much emphasis on this topic. The same can be said about my children's school. I've taught in a few yeshivot, spent time learning in a few of them (kolel, etc.) attended various shuls - very few of them offer lectures (shiurim) on prayer study.
Even without the above adage, which is part of our prayers, many religious Jews are (or should be) aware of the importance of "kavanah" when reciting prayers. Part of "kavanah" means understanding what your saying. I would think that having some knowledge / history would only add to the concentration and appreciation of the prayers.
Why is "iyun tefillah" not a more commonly studied topic in yeshivot and synagogues? Why are there few "organized" shiurim / lectures on prayer?