Christian Ankerstjerne wrote:The problem with RPGs is that, while they may be able to penetrate the armour, they are often not as deadly as a conventional armour-piercing shot.
That and with an effective range of a couple of hundred meters at most (and you better be Muhammed Omar to hit a tank from that range with a Soviet-built RPG), it's going to take some big kahunas to sit still until any armor comes within practical range.
Like many have said above, the Merkava was built to Israeli specifications and has operated admirably. If any aspect of armored warfare is stressed in Israeli tank design, it's protection of the crews. Historically, Israel has always been heavily outnumbered in its conventional conflicts. Ensuring a high survivability rate among the crew is ultimate to everything else. You can always build a new tank, it's a little trickier to train a new crew.
There are a lot of little innovations built into the Merkeva which enhance crew survivability. The Merkava's diesel tanks are lined in between the inner and outer hulls which not only saves additional space but adds protection against HEAT and other shaped charge explosives by dissipating the shaped charge right after it punches through the outer hull. Many Merkevas sport the ball and chains on the turret bustle to pre-detonate shaped charge explosives and deflect, however slightly, AP shot. Deflection of just a few degrees is enough to seriously degrade armor penetration. Some of these aspects of the "superior" Merkava design really aren't that unique and wouldn't necessitate copying Israeli tank designs to implement them.
The front-mounted engine may be harder to service (though the Merkeva is specifically designed for quick in-the-field repairs) but the amount of additional protection added far outweighs its benefits, at least within Israeli armor circles. I imagine have such a layout drastically increases crew survivability in the event the tank sets off a mine or IED (which is still the biggest threat to Israeli armor, despite increasing numbers of AT-14s and other ATGMs supplied to Hezbollah by the Syrians).
The Merkava series was in no small part designed for low-intensity conflicts in urban areas. Perhaps the design has not been more widely developed because the urban-combat role is more suitably filled by smaller, wheeled AFVs with more discriminative firepower, like the U.S. Stryker. Big, heavy, loud, and destructive tanks like the Abrams or Merkeva don't win the hearts and minds of the people caught up in low-intensity conflicts, as our soldiers in Iraq have figured out (the Merkava works well for the Israelis in this role because, well, they don't really mind blowing a lot of stuff up during their operations). MBTs are ultimately much more vulnerable in urban environments because of their ample size and lack of speed than smaller and quicker wheeled armor. The Strykers, for instance, have been dubbed a miracle by many U.S. soldiers returning from Iraq because of their effectiveness in urban areas.
That and perhaps MBT design has reached its pinnacle. Much hasn't changed in the design of modern MBT in the last two or even three decades, and most MBTs fielded by major powers were designed that long ago (save a few like the T-90, but this is exclusively an export model for sale to countries who have few or no domestically-developed MBTs). There seems to be no major push to change MBT design or even add new ones to the stockpile of many major powers. Maybe, as we have discussed heavily on the old forum, MBTs have outlived their legacy and the reason the Merkeva design hasn't been copied is that modern militaries have what they need and aren't anticipating the kind of future for MBTs as they did during the Cold War.
I couldn't find any stats on the survivability rates of Merkava crews, but here's a pretty interesting article on the performance of Merkava during the 2006 conflict in Lebanon.
http://defense-update.com/analysis/lebanon_war_3.htm