Actually, it is not unusual for the heel to be narrower relative to overall width than the forepart. But more importantly, the straight first toe and the straight line along the medial side of the foot from heel to ball is actually a sign of a very healthy foot. We are all born like that (barring congenital anomalies) . Wearing shoes that do not fit force changes to foot that are often irreversible.
That said, while a bespoke fit...esp. in today's market...might be the only option, severe lasts, such as a "banana" shape are not the answer. The "banana" last is for people with foot deformities that force the first toe medially beyond that straight line.
The real problem is that manufactures make shoes for a statistical and market average. Once upon a time, fittings were nearly infinite---many combinations of heel and forepart widths were available. The basic set is A, B, C, D, and E. Yet most manufacturers only produce a D and and E. I don't know of a single RTW maker who offers a full basic range of widths much less the extremes such as AA or EE, etc., or combination fittings either, for that matter. If the stats show that they only sell one pair of A width shoes in a given season, the A width last will be eliminated from what the company offers.
The same holds true for accommodating the straight first toe--manufacturers are responding to the market and so many people have never really and truly been fit. And as a consequence, their feet tend to become permanently set in unhealthy configurations.
But the straight toe configuration is the better and healthier one...so much so that the US military had a a last designed (can't remember what it was called this morning) that was so shaped. And it is still praised and much sought after to this day.
[On edit: I remember the name of the last...it was / is called the "Munson" last. Quite highly regarded even famous.]
edited for punctuation and clarity
Edited by DWFII - 9/3/16 at 9:33am