ASC/DESC and only DESC GRD products

Why there are ASCENDING and DESCENDING orbit pass product for some area and for some other area are only DESCENDING orbit pass products? Is it ok?

the image acquisitions follow a predefined plan. It is updated regularly. You’ll find information about this here:

Observation scenarios
https://sentinel.esa.int/web/sentinel/missions/sentinel-1/observation-scenario

Coverage maps