I've never used a set of drip rails and I'm on triple digit numbers of FE's built.
Back in the 60's, when there was no detergent
oil, the area under the valve covers became caked with sludge. The drains in the heads would be stopped up. The drip rails/tins would be the only way of getting
oil successfully back to the
oil pan.
These days, we have clean oil.
You can leave those tins off (as well as the crank oil slinger and lifter valley pan) and never know any different.