Locus Map Pro is an application with a paid license that is validated upon its first start after installation and then occasionally when updating some additional data. The validation needs internet connection and Google Play Store (or respectively Amazon App Store) installed on your device. This condition does not apply to Locus Map Free.
Do not uninstall Google Play Store or Amazon App Store from your device - your Locus Map Pro will stop working because its licence can not be validated. Without these App Stores you also can not purchase LoCoins in Locus Store and you can not buy your favourite maps.