Apple purged 47,300 broken & outdated App Store titles in October
Apple began its promised purge of the iOS App Store in October, pulling some 47,300 titles, according to third-party research data published on Tuesday.

App removals jumped 238 percent last month, according to intelligence firm Sensor Tower, quoted by TechCrunch. Figures were also about 3.4 times higher than the monthly average between January and September.
About 28 percent of the deleted apps were games, far higher than the next two categories -- Entertainment and Books -- which accounted for just 8.99 and 8.96 percent, respectively. Education came in fourth at 7 percent, while Lifestyle apps represented just 6 percent.
Apple announced plans to start reviewing old apps in early September, "removing apps that no longer function as intended, don't follow current review guidelines, or are outdated." This included deleting "abandoned" titles which hadn't been given compatibility updates "for a long time."

While Apple said that it would immediately remove apps that crash on launch, it added that it would otherwise send out notifications asking developers to update within 30 days if they wanted to keep their apps available.
Purges are likely ongoing, as prior to October, it was estimated that nearly half of iOS apps hadn't been updated since May 2015. Over a quarter hadn't been updated since Nov. 2013.

App removals jumped 238 percent last month, according to intelligence firm Sensor Tower, quoted by TechCrunch. Figures were also about 3.4 times higher than the monthly average between January and September.
About 28 percent of the deleted apps were games, far higher than the next two categories -- Entertainment and Books -- which accounted for just 8.99 and 8.96 percent, respectively. Education came in fourth at 7 percent, while Lifestyle apps represented just 6 percent.
Apple announced plans to start reviewing old apps in early September, "removing apps that no longer function as intended, don't follow current review guidelines, or are outdated." This included deleting "abandoned" titles which hadn't been given compatibility updates "for a long time."

While Apple said that it would immediately remove apps that crash on launch, it added that it would otherwise send out notifications asking developers to update within 30 days if they wanted to keep their apps available.
Purges are likely ongoing, as prior to October, it was estimated that nearly half of iOS apps hadn't been updated since May 2015. Over a quarter hadn't been updated since Nov. 2013.

Comments
What are these monstrosities you are adding to the App Store?
That said, I think the app store should just partition apps/versions by iOS version, and when a certain iOS version hits obsolete, the ability to purchase old versions disappears and only software already purchased can be downloaded. That gives Apple some room to delete software versions that nobody has ever used if they are keeping on top of iOS versions. If someone has an iPhone 4S or an iPad 3, and software is updated to iOS 10 or iOS11 and no longer works on iOS 9.x, then the store should retain the last working version for iOS 9.3.5 and only present the newer version if the iOS device is newer.
Right now the iOS partitions would be
iOS 1.0 - 3.13 (iPhone, iPod Touch 1G)
iOS 4.2.1 (iPhone 3G, iPod Touch 2G)
iOS 5.1.1 (iPod Touch 3G, iPad (original) )
iOS 6.1.6 (iPhone 3GS, iPod Touch 4G) A4 parts with 256MB ram
iOS 7.1.2 (iPhone 4) A4 parts with 512MB ram
iOS 9.3.5 (iPhone 4S, iPod Touch 5G, iPad 2, iPad 3(Retina iPad), iPad Mini) A5 parts.
iOS 10.0+ (iPhone 5 and later, iPod Touch 6G, iPad 4, iPad Air and later, iPad Mini 2 and later, iPad Pro), All A6+ parts
Expect the next obsolescence to bump off the A6 for no ARMv8-A/64bit support, then the A7/A8 parts due to the RAM. Right now the iOS 9.x software still supports 32-bit cpu's and largely the entire reason for obsolescence is the products with it are 5 years old and are ARMv7 instructions. The A6 is ARMv7-A(32bit), the A7 and later all use ARMv8-A (64bit).
So Apple, if it really wanted to, could release iOS 11.0, say 64-bit ARMv8-A only, and that bumps off the A6-series parts, and then there is really no reason to obsolete anything else except for the smaller amounts of RAM on the A7/A8 parts.