Although Marketing is a much broader term and includes sales only as the execution point, why don't most companies differentiate between the two?

it's normal , because most of directors and business owner think that they already professional in marketing it's easy and all about ads social media , booking,...
etc , most of leaders think that we know the competition and the market and we have been in the business for many years, so forget about marketing and focusing on sales

Marketing and Sales must work together, but we have to understand that marketing is a process that enables sales to sell.
Sales is only the final act of business process, but marketing strategy envolves: product, price, place and promotion.
Most companies see marketing as promotion (promotion sales and so on) only, these is the main problem.

Product determining differentiation in sales or marketing activity.
It is essential to differentiate as strategy would get shaped based on the focus.

Marketing is important through its. Advertisement ,promotional activities, awareness programme otherwise who will sale ratger who will be yoyr buyer.