I know it's about different software but ....
Windows 10 will reach the end of support on October 14, 2025, but you can extend support by paying an annual fee. Ahead of the deadline, Microsoft has shared details of Windows 10 extended updates, which may cost up to $61 for enterprises.
It means that legacy cost $$$.
Back to our topic, suppose there would be a migrator for Joomla 3.10 and what next? Would you stay with Joomla 3.10 for the next few months/year, or would you be forced to upgrade J3>J4 anyway? Unfortunately, the life of a webmaster is full of challenges.