I think, competition is forcing FPGA vendors to offer free tools at least for small and medium size FPGA. Lattice e.g. has ispLEVER Starter, operation isn't as intuitively as Altera Quartus, cause it's a combination of different tools (similar to Xilinx ISE), but good quality. https://www.latticesemi.com/products/designsoftware/isplever/ispleverstarter/index.cfm
I think, competition is forcing FPGA vendors to offer free tools at least for small and medium size FPGA. Lattice e.g. has ispLEVER Starter, operation isn't as intuitively as Altera Quartus, cause it's a combination of different tools (similar to Xilinx ISE), but good quality