So, in some works i was browsing recently i found references to 17th century works showing preferred shot-powder ratios for cannons. Here is an one image (for ants) of a table showing it, but there are other instances where you can find similar tables and ratio values.

It seems the weight ratio of shot to powder weight for lower calibres was at that point 1:1 while for higher calibers it rarely goes below half a pound of powder for each pound of cannonball.
E.g. from the table above, the 32-pounder cannon takes 18lbs of powder - more then half its weight in powder. The 24 pounder cannon takes around 14lbs of powder. Smaller calibres are sometimes even have more powder then shot like Falcons of 2-3 pounders who take 3-4 lbs of powder

I then found by browsing the internets that by the 1700s gunners used to have a ratio that appears to be one third of powder to the weight of cannonball, sometimes even one fourth. Like this page gives examples of a 32pounder taking 10.6 lbs of powder and 24pounder taking 8lbs, while this page says later 24-pounders had used 6 pounds of powder. Obviously substantially lower amount of powder then previously.

As I see it, this change can be result of three things:
1) better and stronger powder, either by using a new imporved formula or just better manufacturing process (but the little i looked I don't see anything indicating this. EDIT: also to clarify I am well familiar with corned gunwpoder. The case is, corning was in use since 16th century, so, on surface level, there shouldn't be much difference between cannons used in 1600s and 1700s as both should use corned gunwpoder. yet as shown above they use different powder ratio)
2) better cannon and cannonball design and manufacturing, to have barrels and spherical shots closer to tolerances and with less imperfections for better flight

and finally

3) just from experience or experimentation realizing they don't lose much by reducing the gunpowder weight, or perhaps it is even better, or deciding they can sacrifice range and power (which i am supposing come with more powder) and still do more then enough damage

What would be the real reason for this?