Lyle's Golden Syrup tin design, why is it like this and how to clean it

I suspect you are looking for deep explanations where none exist.

Flat metal work is flexible; by introducing a bend, it becomes stronger. This is the same principal that makes corrugation, and the same reason car parts are all curved. You will note that paint cans have essentially the same design, for the same reason.

The lip around the removable lid is quite likely to be there simply to give it enough strength to allow the lid to be removed and replaced multiple times without distorting the can.

This has nothing to do with the specific product inside.

As to cleaning, a damp paper towel seems ideal. If the lid is well sealed, you could run it under some water to dissolve any caked on syrup, and then dry...

The secret is not to get the lip of the tin dirty. Specifically, do not pour the Golden Syrup out of the tin. Use a spoon or a knife to get out the amount you need. Even if you need to fill a spoon ten times that is quicker than pouring and then having to clean the lip.

In some parts of the world it is sold in jars. The glass threads of the screw lid present much the same cleaning problem though.

It is much simpler to dispense from cans of Golden Syrup if the tin is inverted, and the bottom pierced with a lever can opener - the sort that makes a triangular hole near the edge of the tin, sometimes known as a can "tapper".

You will need two holes opposite one another, the second one to let air into the can to take up the space of the syrup, which can now be poured much more tidily.

The disadvantage, of course, is that you now have to use cling film or similar to keep the contents covered.

The same issue exists with paint cans: the trough in the rim fills up with paint.

Solution there: bang two or three nail holes in the trough so the paint can drain back into the can. The lid will cover the nail holes when replaced.

This should work for syrup too.

I never tip the syrup from the tin but spoon it out using an old tablespoon heated in hot water or over gas flame. The syrup slides off and leaves a clean tin.

I think the 'clean up' issue is finally being addressed by The Powers That Be as in New Zealand you can now purchase golden syrup in plastic squeezy bottles that you simply tilt upside down and squeeze the syrup out, leaving just the tip to clean and enabling a greater degree of accuracy in measuring the syrup.