There are several reasons: First the bridge pickup on the Telecaster has a 15 degree angle perpendicular to the string and the Stratocaster is 10 degrees. There may be other ways of determining the angle but placing theTelecaster plate on the Stratocaster pickguard you can see the difference. The angle of the Telecaster gives the pickup more edge. The bridge pickup on the Stratocaster by passes the tone control and often makes the pickup sound quite bright too.
Players like Eric Johnson rewire the "lever switch" to activate the tone control on the bridge pickup. This way you can roll off some of the high end. The Telecaster uses a copper plated steel elevator plate on the bottom of the bridge pickup. The ferrous plate helps push the magnetic field towards the strings which increases the magnetic field and brightness in the pickup. The bridge and pickup mounting plate are also made of steel which enhances the magnetic field around the pickup. If the steel elevator plate is removed from the Telecaster the pickup and bridge plate become ungrounded. The black wire from the bridge pickup is soldered to the elevator which grounds the strings and bridge plate.
I have often made Stratocaster pickups for Jerry Donahue (Bend-master) using a ferrous bottom plate attached to the bridge pickup of his Strat. It enhances the high end of the pickup and helps make it sound more like a Telecaster. If you try it, make sure you insulate with masking tape between the pickup and steel plate and also make sure it is grounded. Silicone can be used to help keep the plate in place and reduce microphonic feedback.
WRITTEN ON JUNE 12, 2015, BY