What does “all extensions” mean? Is it all the gTLDs, the ccTLDs, the 2L ccTLDs? You're talking about hundreds of names here. Then all the typos, hyphens, etc. You're looking at thousands, perhaps tens of thousands, of names. The reg fees alone could easily run to 100k, not to mention the overheads of running the “Domain Department” that manages them all. And, of course, since many ccTLDs have residency requirements the cost of setting up a corporation in each country. Even if they're not trading. the yearly maintenance charges for a few dozen companies will run you more than the reg fees.
So you're potentially looking at $1M/year to protect against cybersquatters who you have to deal with a few times a year at a cost of what $10K each? It's not economical.
Most very large companies get the .com, .net, and ccTLD of the countries they do business in. But I think that's mainly because they actually use them.