Because I have to pay that monthly fee unintentionally to be able to work with UE4 already anyway? I was in my happy Blender world for a while and planned to spend further 30€ in the UE Marketplace early this month but had to stop because I struggled around a very annoying bug in animations based on Epics third person template ( Animation Blend Per Bool Issue - Weird Pop or Jump or something.. - Character & Animation - Epic Developer Community Forums ) and had to rent MayaLT instead to fix this. Most likely Autodesk is getting that 30€ next month instead of UE marktplace as well (no kidding).
Export [Insert your favourite 3D tool] to UE4 works.
Export from UE4 back? My experience so far: It’s either Autodesk or nothing.
Cheapest thing without the requirement to sell my body I could get (even comparing competitors like C4D, Modo, …) is MayaLT and that’s already enough for Stingray. I know Stingray too less to switch today but as you could see I started informing me already. Guess why? I’m pretty sure Stingray would make some progress month for month as well. I would get advertisment from them months for months because I’m doomed to use a 3D tool that I’m only medicore happy with but since I have to pay it already anway I would try to use it further and get as much value for my money as possible. After watching hours of tutorials learning Maya LT I know already spacebar and right mouse button are my friends and that the control rig creation is way easier in MayaLT than in Blender (nice). But I had my control rig finished in Blender thanks to lots of good tutorials anyway and I’m in doubt if I would ever be close to Blender workspeed for moddeling, weight painting, animating… in Maya. For example I hate it that 3 keys in Maya are wasted for only switching between rotation and translation and I’m still not able to switch from world to object rotation using this or another key like hitting “r” and twice “y” or “z” in Blender. And while I could change the rotation-speed via the distance to the center in Blender it seems I’ve to pull around that anoying gizmos again and again. It feels a bit like forcing a VIM-fanboy into some medicore tweaked GUI. I would not be “fast” with hitting spacebar after moving my mouse over a view first because it feels still slower than using just numpad 1 3 5 7 in Blender.
Conclusion: It’s the fault of Epic (and the lack of alternative export formats to FBX) and Blenders GPL (that makes good FBX support hard: Blender FBX Import - Blender and CG Discussions - Blender Artists Community) that I know Stingray today. FBX is the only format that works as UE4 export and while there are many programs that could export FBX very well the import (especially of animations) drives you in the spread arms of Autodesk 
- And maybe you already heard about it: They have Stingray for you now as well. 
- I would prefer to pay for a solid *.blender export from UE4 (or *.fbx importer for Blender) instead renting Maya LT and getting informed about and being able to use Stingray month for month. But …