Supporting LongBlob / LongBinary in Craft record ColumnType
Why is LongText supported but not LongBlob for Craft records?


Support, mainly... and there hasn't been a demand for it (you're the first to ask that I'm aware of).

Currently Craft's PHP based database backup logic chokes on MySQL datatypes that can't be represented as textual data.

For the upcoming Craft 3, we've done away with the AttributeType magic and you've got more direct/exact control over how your want your schema to be defined.

We also plan on updating the backup logic to be able to handle non-textual datatypes.

In the meantime, if you want this in Craft 2, you'll have to move that attribute/column out of an Active Record, create it with a migration and have your service layer use DbCommand to interact with it.