Yes, you can use alternatives but kite tubes are specially formulated to withstand heat and UV rays which will make them last longer.
And no, it's not a gimmick, it's a fact. Rubber tubes you buy in store are not made for outdoor use. However, they will work and you may not notice the difference in just a few years.
We sell Airush ones on our website (larger diameter) in case you need those. Cost about $60 delivered for 5x 25cm tubes
www.kitebud.com.au/product/airush-strut-tube-one-pump-hose/