XLSX files don’t follow any contact standard. They’re just rows and columns with no enforced meaning. Mobile operating systems like Android and iOS expect contacts in a structured format where each data point has a defined role. When you try to import spreadsheet contacts directly, the phone has to guess which column is a mobile number, which is work and which text is a note. That guesswork often fails, which is why imports get rejected or load incorrectly. Tools such as Softaken Excel to vCard Converter solve this by converting spreadsheet data into a proper vCard contact format that mobile devices are designed to read without interpretation.