Your co-worker is wrong.
The grounding screw was added to switches to alleviate a possible shock hazard, in case the switch should fail in a peculiar manner. Older wiring is, as you have read, grandfathered to not require this ground connection.
However:
Your switch may be grounded anyway. If you have armored cable in your home, type AC which is commonly referred to as BX, the armor sheath provides a grounding connection from the main panel to the junction box and the screws attaching the switch to the box provide the final connection. A grounding pigtail from that screw on the switch to the box, there's usually a tapped screw hole in the back, is a more reliable final connection.

Here's the operative part of the code. See the exception.

(B) Grounding. Snap switches, including dimmer and similar control switches, shall be connected to an equipment grounding conductor and shall provide a means to connect metal faceplates to the equipment grounding conductor, whether or not a metal faceplate is installed. Snap switches shall be considered to be part of an effective ground-fault current path if either of the following conditions is met: See related UL

(1) The switch is mounted with metal screws to a metal box or metal cover that is connected to an equipment grounding conductor or to a nonmetallic box with integral means for connecting to an equipment grounding conductor.

(2) An equipment grounding conductor or equipment bonding jumper is connected to an equipment grounding termination of the snap switch.

Exception No. 1 to (B): Where no means exists within the snap-switch enclosure for connecting to the equipment grounding conductor, or where the wiring method does not include or provide an equipment grounding conductor, a snap switch without a connection to an equipment grounding conductor shall be permitted for replacement purposes only. A snap switch wired under the provisions of this exception and located within 2.5 m (8 ft) vertically, or 1.5 m (5 ft) horizontally, of ground or exposed grounded metal objects shall be provided with a faceplate of nonconducting noncombustible material with nonmetallic attachment screws, unless the switch mounting strap or yoke is nonmetallic or the circuit is protected by a ground-fault circuit interrupter.

Thank you so much.....I feel much better now

"I have been reading online and it seems this is not a requirement for older homes. "

Depends what you mean by "older". 30 yrs? 50 yrs? 100 yrs? Also, we the receptacles etc updated with grounds?

As a general rule, anything original is grandfathered in. If you start making any significant changes or renovations, you would be required to bring that portion of your electrical system up to modern standards.

As to the safety aspect - yes, grounding is a safety improvement. If the wiring in your home is old enough not to have this feature, it likely doesn't have other modern safety features either. That doesn't mean it is a deathtrap or something, but it is something to consider for future improvement.