Why is there such little memory in electronics?

You would think by now there would be more than just a 16, 32 and 64gb option for most devices. Considering 64gb can fit into a small SD card why can't an iphone have a couple hundred gb of memory in it. Or an ipad as well. It doesn't make any sense.

Well from what I know the smaller the chip is the more memory is in it

Because who the hell would carry around 100GB of stuff on a phone?

COST.

SD Cards have an infinitely slower I/O (input/output) speed than flash storage that is used in these devices.
Whilst an SD card can transfer at a few MB/s, the storage in the device can transfer at easily 100MB/s. Speed is the main priority; phone processors have to be slow already, having a bottleneck on the speed of data transfer would be horrible for system performance.

Here, let me show you what I mean:

Hard drive:
http://www.tigerdirect.ca/applications/SearchTools/item-details.asp?EdpNo=7739052&csid=_61
Cost: 189$
Storage: 4096GB
Speed: 70MB/s (based on averages for 5400RPM HDDs)

SSD:
http://www.tigerdirect.ca/applications/SearchTools/item-details.asp?EdpNo=5552077&csid=_61
Cost: 199$
Storage: 256GB
Speed: 530MB/s

Look, the HDD gives you SIXTEEN TIMES the storage of an SSD, and the SSD costs more! But whilst the HDD is 16 times larger, the SSD is nearly 8x faster. There's always a tradeoff between speed and size.

Also, you actually can get 128GB on a phone, by getting a 64GB Galaxy S3 and putting a 64GB microSD card inside it.

To answer your question simply: the reason we have small storage capacities is due to the fact that speed is a more important factor than raw space. Also, conventional hard drives (which offer more space) have moving parts, which are hundreds of times more likely to break when dropped/exposed to impact, which would mean that even a slight bump could render a phone useless.