VEGF is a family of growth factors that promote angiogenesis and vasculogenesis.
Vascularization is a key step in the progression of cancer, so the VEGF family has often been a target for suppression: preventing vascularization of tumors can stop their further growth.
That said, your premise that VEGF hasn't been tried clinically is false: there have been several clinical trials of VEGF (and no doubt more that I didn't find).
Hedman, et al 2003 used catheter-based VEGF gene transfer at the time of angioplasty/stenting, though they found it did not prevent restenosis they did see increased perfusion (it seems to me that further research didn't show sufficient effects on long-term outcomes). Ripa, et al 2006 used VEGF gene transfer as part of a treatment for ischemic heart disease. It seemed like the treatment was safe, but the efficacy was limited. Ropper, et al. 2009 attempted VEGF gene transfer for the treatment of diabetic polyneuropathy. They found some improvement of pain, and report a fairly high rate of adverse events but their control group also experienced adverse events.
It seems like a similar VEGF plasmid is available in Russia as Neovasculgen for use in limb ischemia; the company developing the drug is in the process of beginning to get approval elsewhere.
VEGF as a topical application has been studied under the name telbermin, for example Hanft, et al 2008.
There may be others, but I stopped my search there. https://clinicaltrials.gov/ is a good place to start looking for what research has been done in humans if you have trouble finding journal articles at first.
Hanft, J. R., Pollak, R. A., Barbul, A., Gils, C. V., Kwon, P. S., Gray, S. M., ... & Breen, T. J. (2008). Phase I trial on the safety of topical rhVEGF on chronic neuropathic diabetic foot ulcers. Journal of wound care, 17(1), 30-37.
Hedman, M., Hartikainen, J., Syvänne, M., Stjernvall, J., Hedman, A., Kivelä, A., ... & Närvänen, O. (2003). Safety and feasibility of catheter-based local intracoronary vascular endothelial growth factor gene transfer in the prevention of postangioplasty and in-stent restenosis and in the treatment of chronic myocardial ischemia: phase II results of the Kuopio Angiogenesis Trial (KAT). Circulation, 107(21), 2677-2683.
Ripa, R. S., Wang, Y., Jørgensen, E., Johnsen, H. E., Hesse, B., & Kastrup, J. (2006). Intramyocardial injection of vascular endothelial growth factor-A165 plasmid followed by granulocyte-colony stimulating factor to induce angiogenesis in patients with severe chronic ischaemic heart disease. European heart journal, 27(15), 1785-1792.
Ropper, A. H., Gorson, K. C., Gooch, C. L., Weinberg, D. H., Pieczek, A., Ware, J. H., ... & Kirchmair, R. (2009). Vascular endothelial growth factor gene transfer for diabetic polyneuropathy: a randomized, double‐blinded trial. Annals of neurology, 65(4), 386-393.
Simovic, D., Isner, J. M., Ropper, A. H., Pieczek, A., & Weinberg, D. H. (2001). Improvement in chronic ischemic neuropathy after intramuscular phVEGF165 gene transfer in patients with critical limb ischemia. Archives of neurology, 58(5), 761-768.