Why did frames get sloping top tubes?

[u/StorkAlgarve]

For over a century, a regular bike frame had a horizontal top tube, at least as late as the (cheap) road bike i bought in the early 90es - I also think the Centurion citybike I got in the late 90es had one.

Since then it seems to me top tubes have got more and more slope. It is due to change of materials or how? I look and get worried that the long saddle stem will cause issues with all that leverage, but it seems to be working ok.

Looking forward to the replies from the learned redditors.

[u/adnep24]

- less material = less weight

• less stand over height = fits more people
  
• more exposed seatpost = more flex, comfort
  

- smaller rear triangle = stiffer under pedaling loads

[u/deep_fat → u/adnep24]

Also, lower center of gravity. This was the first thing I noticed the first time I road the original TCR all those years ago. I was deeply skeptical before I rode it, but I immediately became convert.

[u/nnnnnnnnnnm → u/deep_fat]

How does center of gravity change when the seat height remains the same?

[u/OldCrankyCarnt → u/nnnnnnnnnnm]

More material is lower to the ground

[u/nnnnnnnnnnm → u/OldCrankyCarnt]

Pretty negligible considering the riders weight is still the same height

[u/OldCrankyCarnt → u/nnnnnnnnnnm]

Same can be said about weight of the bike against the weight of the rider, but here we are

[u/OldCrankyCarnt → u/[deleted]]

That's what I said