Why would my dependency visa only be issued for 3 months instead of a year?

The user has applied for a dependency visa in Thailand following her husband's employment and was initially informed that she would receive a visa stamp in three weeks. However, she was later told that the visa granted could only be valid for three months, requiring her to reapply for a one-year extension thereafter. A comment explains that the initial visa is typically a 90-day non-immigration visa, and she cannot apply for the one-year extension until she is on the correct visa type, meaning she would have to wait a year to apply for the extension alongside her husband.