While there is a possibility that sharp things cause those punctures in your tyres, it is highly unlikely with the frequency. You would have to accept that there is something wrong with your tyres or the method you manually repair them. Here are two possible causes of your flat tyres that always require puncture repairs.
You have a worn out tyre.
Threads are those fibres that make up the foundation of your tyre. These threads could be unprotected if your tyre rubber is overused. When this occurs, your tyre is more vulnerable to puncture and tearing. If the casing does split, the protection for flat is lowered, and the tube can expand more than its typical dimensions.
Repair this by switching tyres because exposed threads mean dead tyres. Although, it would be better just to change your tyres before it even reaches this point. Replace your tyres when you see the rubber at the crest begin to crown and lose its round shape.
You hit an object on the road or drive with low tyre pressure.
In this situation, you have pinch flats. If you drive with a low-pressure tyre and then you bump into an object or a pothole in the road, your tyre will shift against the rim. It will then break from the impact of the road and the wheel.
Repair this by regularly inflating your tires. Broad tires and wide wheels will function on low pressure, below 80PSI depending on the weight of the driver. However, you have to regularly inflate common narrow wheels that have 23c tires for around 100PSI or more.
There will come a day when you will get fed up with the hassle recurring flat tyres bring. Ensure that your tyres are more reliable by examining the above possible causes.