Your scalp and the ends of your hair are, in practical terms, two different surfaces that happen to be attached.
That explains the thing most men notice by Thursday: roots looking greasy, lengths looking dull and rough, and no single product that seems to sort both. It isn't a contradiction, and it usually isn't the shampoo's fault. It's anatomy.
Oil is made in the skin, not the hair
Sebum comes from sebaceous glands, and those glands sit in the skin, attached to the hair follicles. The scalp carries one of the densest concentrations of them on the body, alongside the face, chest, and upper back. Each gland empties into the follicle, so the oil surfaces exactly where the hair leaves the skin.
The hair itself is dead keratin. No glands, no blood supply, no way of making anything. Every bit of oil on the shaft either travelled up from the root or came out of a bottle.
How much sebum you produce is largely set by hormones and genetics — androgens are the main driver, which is why men tend to run oilier, and why the level doesn't shift much week to week regardless of what you buy.
Why the ends never catch up
Sebum travels along the shaft slowly, and mostly by contact: brushing, hands through the hair, a shirt collar, a pillow. Nothing pumps it outwards. The old advice about brushing hair through properly every night wasn't about stimulation or circulation — it was oil distribution, and on that narrow point it was right.
What you get is a gradient. The root sits in it. A few centimetres out, there's less. Past that, less again. On anything longer than a crop, the ends are effectively unsupplied.
They are also the oldest part of the hair. The last few centimetres have survived every wash, towel dry, hot shower, and rub against a jacket collar since they grew, and unlike skin, hair cannot repair itself. The cuticle — the layer of overlapping scales on the outside of each strand — lifts and chips under that wear. Lifted scales scatter light instead of reflecting it, which is why worn hair looks dull as well as feeling coarse. Dry ends aren't thirsty. They're eroded.
Short hair compresses the problem
Keep your hair short and the gradient barely has room to form. The whole length sits close to the source, which is why short hair tends to look uniformly oily rather than oily on top and rough below. The trade-off is that the ends are new, so genuinely worn lengths are rare on men who get cut every four weeks.
What short hair does instead is leave the scalp exposed — to weather, to shower temperature, and to whatever you wash with. So for most men the real pairing isn't oily roots and dry ends. It's an oily scalp and a scalp that feels tight and reactive, often in the same week. Same skin, over-corrected.
Wash the scalp, condition the hair
This is the part that changes the result, and it costs nothing.
Shampoo is for skin. Work it into the scalp with your fingertips, not your nails, and give it long enough to actually do something, which is longer than most men allow. The lengths get cleaned perfectly well by what rinses down through them; they don't need their own scrub. The Doers of London Shampoo is built as a balancing daily wash for that job, which matters considerably more than how much lather you can generate.
Conditioner is for the hair, and specifically for the part the oil never reaches. Mid-lengths and ends, nothing above the ears. Run Conditioner through your roots and you will flatten hair that was already carrying plenty of its own oil.
Resist the urge to solve oil with heat or frequency, too. Very hot water and hard washing won't reduce what the glands produce, because that output is hormonal — but they will rough up the cuticle and leave the scalp tight. Warm water, scalp focus, and consistency get further than force.
One more thing worth separating out. Oiliness is a normal property of scalp skin. Persistent itching, flaking that keeps returning, or a scalp that feels sore is a different question altogether, and better raised with a GP or dermatologist than solved with another bottle.