Why doesn't Apple put bigger trackpads on bigger laptops? (+concepts)

Introduction

I first took serious notice of how much space there is around the trackpad on my 15" Macbook Pro a few days ago, when I was zoning out while writing an essay. For those who may not know, Apple uses the same trackpad on all of their Pro laptops: the 13", 15", and even the old 17". They are (roughly) 3" and 4.125" wide. This size fills the palm rest (vertically) on a 13" Macbook Pro, but on the 15" and 17", there is a strip of aluminum on the top of bottom of the trackpad.

This forum post is twofold: First, I want to simply ask "why" Apple does this. As my title suggests, I can't think of a good reason for Apple not to put a bigger trackpad where they could. Having more space is just better to have and easier to use. Perhaps you know the answer to this question, and I would love to hear it! Secondly, I want to be hypothetical, and look at what the size of a trackpad would be if Apple were to fill up the palm rest (vertically, again) of a 15" or 17" laptop while keeping the same proportions on the trackpad.

Part 1: Why Not?

As I mentioned in the introduction to this piece, I don't know why Apple doesn't make bigger trackpads. My biggest reasoning for questioning this is simply because there appears to be enough space for one. I would argue that Apple make some of (if not, the best) trackpads in the world. Multitouch gestures make such a difference when trying to work more efficiently, and the size of their existing trackpad is relatively larger than most PC manufacturers' trackpads. However, more space for inputs would never be a bad thing, and that's the idea that I'm poking at.

I can think of two possible "reasons" why Apple might do what they do now. The first is cost (as in, "it costs Apple too much to make a trackpad that big"), and the second is manufacturing limits (as in, "Apple wouldn't be able to produce large trackpads in volume").

For both of those points, there is one reason that invalidates the argument. That reason is the Apple Magic Trackpad:

Apple_magic_trackpad

This product is even larger than any of the hypothetical trackpads that I will get to in a moment, yet Apple still ships them in volume and at a relatively affordable price.

Because of this lack of an answer, I am puzzled. Again, I ask the fine people in the Apple Core: "Why doesn't Apple put bigger trackpads on bigger laptops?"

Part 2: What If?

Let's say that, for whatever reason, there was in fact no problem with Apple putting in a larger trackpad. Let's also so that because it would be such a great upgrade, that they did. What would something like that look like?

15" Macbook Pro

Here is the current 15" Macbook Pro (non-Retina), with the standard-sized Trackpad:

15old_medium

Here is the same laptop, with the trackpad as big as it can fit at the same proportions:

15new_medium

Finally, here are the two overlaid on each other:

15mix_medium

The "new" trackpad would be about 4" high and about 5.5" wide, and increase in surface area of about 78%.

17" Macbook Pro

Just for fun, how big would such a trackpad end up being on a 17" Macbook, if they still made them? Well, first of all, here is the most recent 17" Macbook Pro's trackpad:

17old_medium

Here would be the maxed-out trackpad on a 17":

17new_medium

And finally, here are the two overlaid:

17mix_medium

Such a trackpad would be a massive 4.333" tall and 6" wide, and the surface area would be 110% larger. Not bad!

Conclusion

Alright - I've talked enough. I asked my question and I laid out a few speculative scenarios. Now I'm curious about what you guys think. Thanks for reading!

Some random disclaimers

1) My math is heavily based on rounding, guessing, and saying "ehh... close enough." That said, I'll bet that my measurements and math are probably off by a bit. Please feel free to prove me wrong by a fraction of an inch. For the purposes of such an article, I would say that my math is, indeed, close enough.

2) My knowledge of Photoshop is minimal. The pictures I put together aren't perfect, but the get the job done. Similarly, I guess you could say that they're "good enough." ;)