Organizations often retain legacy systems instead of fully retiring them is correct.

Organizations often retain legacy systems instead of fully retiring them creates fragmentation because older systems are costly and risky to replace and because they often have deep integrations and custom data flows that prevent simple consolidation. Migration projects compete for budget and staff and they require extensive testing so many organizations choose to keep legacy systems running while layering newer architectures on top.

Legacy systems also remain because of regulatory requirements and vendor lock in and because business units rely on specific functionality that is not available or fully tested in modern replacements. That combination of technical debt and organizational inertia leads to a heterogeneous environment more often than the other reasons listed.

The adoption of multiple cloud platforms and services increases architectural diversity is incorrect because using multiple clouds is a modern, often intentional strategy that produces diversity by design and it does not explain the persistent presence of old, hard to retire systems. Cloud diversity can be managed with governance and automation whereas legacy retention creates long lived fragmentation.

Development teams prefer bespoke creative solutions for distinct problems is incorrect because bespoke solutions may add variation but they are usually created for specific needs and can be consolidated over time. The widespread fragmentation in enterprises is more commonly driven by systems that were never retired than by developers choosing custom approaches.

Rapid changes in technology create complexity that is difficult to manage is incorrect because technological change can increase complexity but it does not by itself explain why old systems remain in production. The key factor is the decision or inability to decommission older systems which keeps multiple architectures in place.

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