Not all points are equal in value. Venture miles is not comparable to Amex MR, since the value of MR can vary wildly depending on how you are redeeming them.
Last year, I redeemed 90k MR points, transferred to Aeroplan, to fly business to Thailand... the actual cost of the flight was well over $7000 if paid for by cash. Redeeming business to Japan through ANA cost 65K MR to ANA, flights can easily run $3-4000.
Venture earns at 2x, but the most you can get out of them is 1 cent per point (unless something has changed and I am not up to date on how to use them). Let's take my example of 90k redemption to Thailand, it would take 700,000 Venture points to pay for that, earning at 2x, means $350,000 spent. Using the Amex EDP and taking advantage of the 3x category and 50% bonus, I could spend about $20,000 and get enough MR to pay for that ticket. That's not a very high level of spend at all.
If you are flying coach around the US, then it might not make sense to you... but your spending habits could actually be allowing you to fly in business or first class. Most of my flying is international and I haven't redeemed points for a domestic flight for years, since the redemption value is low and I can make better use of those points for an international business or first class trip. It's opportunity cost - I can either pay for the ticket, earn MR at 3x and use them later at 6cpp+ or I can redeem for around 1cpp or 2cpp and not earn any miles. For people who can't afford the flight and don't have any plans to fly internationally, then redeeming for lower value can make sense, so I guess the Venture would make sense in that case.
What is best for you isn't the best for everyone else, however.