We = Datadirect, now part of Progress. IBM provided drivers for SQL Server because they recognized that some WebSphere App Server shops wanted to use WAS, but needed to talk to SQL Server. So IBM opted to provide a total solution.
ftp://ftp.software.ibm.com/software/websphere/info/tools/DataDirect/datadirect.htm
From the above link, including the typo re "connectivy":
IBM WebSphere Connect JDBC and SequeLink JDBC Drivers
Abstract
This page provides updates for JDBC drivers shipped with WebSphere Application Server to enable connectivy to the Microsoft SQL Server database.
WebSphere Connect JDBC driver
WebSphere SequeLink JDBC driver
Applicability
WebSphere Application Server releases:
6.1.0.x
6.0.2.x
5.1.1.x
It's the same reason Oracle ships drivers to non-Oracle database with their App Server product.
"This chapter provides information about the WebLogic-branded DataDirect drivers that are included in the WebLogic Server installation.
Oracle provides WebLogic-branded versions of DataDirect drivers for DB2, Informix, MS SQL Server, and Sybase. Review the following sections for information on how WebLogic-branded DataDirect drivers are configured and used in a WebLogic Server environment. For detailed information on these drivers, see "Progress DataDirect for JDBC User's Guide Release 4.2" and "Progress DataDirect for JDBC Reference Release 4.2" at
http://www.datadirect.com/index.html..."
http://docs.oracle.com/cd/E28280_01/web.1111/e13726/dd.htm