Are the old Fiqh books—especially those of the Maliki school—which mention rulings without evidence, devoid of evidence, or did their authors know the evidence but omitted it for brevity?

The early generations of the Muslim Ummah used to mention issues and their proofs in their writings, as Malik did in "Al-Muwatta'" and Al-Bukhari in his "Sahih." Subsequent eras saw authors compiling jurisprudential issues; some mentioned the proofs, such as Ibn Abd al-Barr in "Al-Istidhkar" and Ibn Qudamah in "Al-Mughni," while others limited themselves to mentioning the issues without their proofs for brevity, as did Ibn Juzayy in "Al-Qawanin" and Al-Nawawi in "Al-Rawdah," although they focused on proofs in more extensive works.