Lonely Planet's Mongolian Phrasebook & Dictionary has only 212 pages, while Japanese has 272 pages, and Chinese has 256 pages. Also, the Mongolian phrasebook does not have some sections that other phrasebooks have. (In fairness, the phrasebook also has some sections that are specifically about Mongolian topics)
Is this because Mongolian phrasebooks are less commonly purchased than other languages, and they deal with the reduced revenue by creating less content?
Am I likely to encounter this with other Lonely Planet phrasebooks about less popular languages, and/or with other publishers' phrasebooks about Mongolian?