You are correct: 1 Pound (Lb) = 4.448 Newtons (N)

However the common measure of mass is pounds-mass (Lbm). Compare:

1 slug = 14.59 kg
1 kg = 2.204 Lbm

You can see how the slug is just too big for ordinary people to use... A full-grown man's mass would be only about 6 slugs. Should we quote it to people, or fill out forms with 3 decimal accuracy, or switch to a different unit? What if I were measuring small amounts of food, say, for cooking recipes, weighing a prize fish, or even themselves. In human terms even kilograms (kg) are sometimes too large and impractical a unit of measure. Although it is easier to use metric for calculations it is often better to show results in imperial units as well as metric. I personally wait until I've finished calculations before displaying results in both systems. The type of situation usually dictates the units used, although they are often interchangeable with other measures. Pounds-mass fits into a group of units referred to as "Common Measures", just as certain frequently-used quantities of foods are commonly measured out in teaspoons, 1/2-cups, or quarts.

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