Because a BLOB/TEXT field type is meant for a very large amount of data. PHPMyAdmin is trying to help you by not automatically displaying what would likely be a large amount of text in a table output - which would likely make the page unreadable. Let's say you were storing the text for an entire report in that field. It would be stupid to output that in the DB management display.
If you are not storing LARGE amounts of text in that field you should by using something like VARCHAR with a limit on the number of characters.
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