Convenience. Number of required pins for 8-bit CPU is usually low. Rectangular package is smaller/cheaper to make and can be socketed.

Hi, I don't know for sure, but maybe due to the manufacturing process and or the board raster.
Originally, ICs were round (like transistors; TO-39,TO-18); like the original 741 op amp or 555 timer ic.
Later, they were made with the help of inductive furnances, maybe that's because things became more rectangular, dunno.
The high amount of pins and the standard circuit board rasters (pin spacing) may also influenced the shape of the semiconductors.
These are just some ideas, though. Maybe some other Vogons have a better explanation. I'm simply too young, I'm afraid. 😅

Having pins on two sides is simpler than 4 sides. Easier to add/remove from sockets too. Rectangles have greater edge length overall than squares.

The 80286/80186 era used CLCC, too, though.
ZIF sockets in general were not cheap to produce, on the other hand.

The Motorola 68000/68010 was an extreme example of a CPU that used DIP/DIL, by the way. 😁

One of the issues with rectangular packages is the uneven length of bond wires, which becomes an increasing issue with speed ..

The finished silicon disc had to be diced in squares or rectangular.

Long rectangular IC is worst on real estate and packaging design, distance from bond point to the pin is all uneven effects the timing especially at high frequency. Best compact, even lengths are squares even the BGA.

Electrons travel time is 11 inches for one ns.

Cheers,

Fuck BGA all my homies hate BGA

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Makes perfect sense, and they look pretty easy to lift out compared to their more modern counterparts. Really cool to see how far we've come from then, and even from when I started my account here in 2004 at 13, and to think in that time technology has gone from one core at 3.5 Ghz to 6-8 cores at even higher speeds for each core, and the faster RAM we have these days. I'm going to be 30 this year; I think this is the longest I've had an account anywhere and glad to be posting about retro hardware to this day; classics never die! 😀

Ribbon style manufacturing gives you flat pins on the edge of the chip

Cheap easy but likely not dense enough when pin counts gets into the hundreds

Have absolutely no f*&^#@ idea at all...

Wait a minute. .......
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Nobody likes squares!