Rajdhanis mainly run via RNY because it is the shorter, hence faster and more preferred route. Also the RNY route is much more populous, with major towns like Nalbari, Barpeta on the section, hence major daily trains like Avadh Assam, Brahmaputra, Kamrup, North East, Kanchanjungha all run through RNY section. GLPT section is scarcely populated plus longer, hence there are less trains through GLPT