BLOBs, CLOBs and NCLOBs are fully materialised into a single byte[]/String. In the case of large content (imagine a file stored in a BLOB) this puts quite a lot of pressure on both the allocator and the heap. It also defeats the point of streaming. Consider the following use case:

try (InputStream stream = resultSet.getBlob("column_name").getBinaryStream()) {
    // stream content
}