As has been pointed out, technology is not an "on/off" switch. Gunpowder weapons have been used in warfare in Europe since the 15th century, yet in the 20th century, bayonets and sabres still saw use in the trenches. Why? Because in many situations, they were still the superior weapons. Tanks and bayonets still coexist today. Having one doesn't mean you can't put the other to good use.
Bows were not replaced by muskets because the muskets were better; in fact, the bow was a far superior weapon with better range, penetration, and rate of fire. The catch was that using a bow well is hard while using a musket decently is really easy. So if you could use a bow, that was far superior. If you couldn't, you'd get by okay with a gunpowder weapon (or crossbow). It wasn't until the 19th century that firearms actually became better than bows, and that's more than 400 years after gunpowder weapons first appeared on battlefields.
The same goes for pretty much any other technology - steam locomotives and horse-drawn carriages coexisted. Many ships would have both sails and steam propellers. There are plenty of examples of things like fire engines where the pump was steam powered, but that pump was placed on a horse-drawn carriage. Because the steam engine was great for pumping water, but horses were cheaper and faster for transporting the engine around. The cheapness is especially relevant - just because there exists a machine that can do something better, that doesn't mean that the machine is the better option.