Acoustic Guitar Is Different with Electrical Guitar: Quantity of Frets

Acoustic Guitar Has Less Frets
In a short word, acoustic guitar normally has 18-20 frets which is less than 21 frets (minimum) of electrical guitar. 
This is an interesting phenomenon. We hope that you are just as curious as we do to find out why. 
First comes to our mind is that it is due to the traditional design of the acoustic guitar. And we think it is better to start at classical acoustic guitar. Because when classical guitar appears, let’s say, the compositions for classical guitars required less technique to make vibration from high position. 
Another reason is the size of the body. As we can figure out by our eyes, acoustic guitar or classical guitar has bigger sized body than electrical guitar. Therefore, it won’t allow to play at the upper position so frequently. 
And there are many other reasons. In this article, we are trying to share as much as we can.

Acoustic Guitar Body Size Is Bigger
Visually, we all can tell that most of the electrical guitar body are smaller than acoustic guitar body and classical guitars.
In our opinion, because the vibration is created by electronic system of the electric guitar. In other word, tonewood material doesn’t play a primary role like acoustic guitar. We have posted some articles to explain the impact of tonewood on acoustic guitars, if interested, you can visit: Custom Built Guitars: Tonal Influence of Back & Side and Acoustic Guitar Body: Key Part of Guitar for reference.
The Differences Between the Neck Joints
It is a common sense that most of the acoustic guitar necks joint the bodies at the 14th fret, although less joint at the 12th fret. Thus, it is difficult to access the upper position which start from 15th fret. Just look at our hands, we are sure most of us are born with normal-sized hands. It is no point for an acoustic guitar has more than 20 frets. 
Typically, electric guitar neck joints the body at 17th fret. With cutaway body (or with two horns like ST guitar), it allows to access the upper position easily and comfortably. For some brand of electric guitar, the neck joints the body even at 20th fret. 
Beside the designation, we assume that this is related with the scale length, too. Since acoustic guitar and electric guitar share the same scale length, typically 650mm, with smaller body, electric guitar neck should joint the body from a higher position.  We will leave this math to you. 
Why Less Upper Fret Access of Acoustic Guitar?
Since the sound of acoustic guitar is heavily relied on the resonation of soundboard. And the vibration quality relies on the distance between soundboard and frets, the longer the distance, the more sufficient vibration the string. Thus, it is meaningless to access an extreme upper position of acoustic guitar. 
Remember that we have mentioned the sound of electric guitar is mainly relied on the electronic system like pickups, etc. Thus, when access a higher position to make the vibration, the sound could still be unique and beautiful.
We are very glad to hear from you for different opinion, especially, if you have any special needs to custom guitar with us, it is better to CONTACT US to figure out if the solution is right for you.